/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.hadoop.mapred;

import java.io.IOException;
import java.net.BindException;
import java.net.InetSocketAddress;
import java.net.UnknownHostException;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.Date;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.Properties;
import java.util.Set;
import java.util.TreeMap;
import java.util.TreeSet;
import java.util.Vector;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.CopyOnWriteArrayList;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FSDataInputStream;
import org.apache.hadoop.fs.FSDataOutputStream;
import org.apache.hadoop.fs.FileStatus;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.fs.permission.FsPermission;
import org.apache.hadoop.http.HttpServer;
import org.apache.hadoop.ipc.RPC;
import org.apache.hadoop.ipc.Server;
import org.apache.hadoop.ipc.RPC.VersionMismatch;
import org.apache.hadoop.mapred.JobHistory.Keys;
import org.apache.hadoop.mapred.JobHistory.Listener;
import org.apache.hadoop.mapred.JobHistory.Values;
import org.apache.hadoop.mapred.JobInProgress.KillInterruptedException;
import org.apache.hadoop.mapred.JobStatusChangeEvent.EventType;
import org.apache.hadoop.net.DNSToSwitchMapping;
import org.apache.hadoop.net.NetUtils;
import org.apache.hadoop.net.NetworkTopology;
import org.apache.hadoop.net.Node;
import org.apache.hadoop.net.NodeBase;
import org.apache.hadoop.net.ScriptBasedMapping;
import org.apache.hadoop.security.AccessControlException;
import org.apache.hadoop.security.SecurityUtil;
import org.apache.hadoop.security.UserGroupInformation;
import org.apache.hadoop.security.authorize.AuthorizationException;
import org.apache.hadoop.security.authorize.ConfiguredPolicy;
import org.apache.hadoop.security.authorize.PolicyProvider;
import org.apache.hadoop.security.authorize.RefreshAuthorizationPolicyProtocol;
import org.apache.hadoop.security.authorize.ServiceAuthorizationManager;
import org.apache.hadoop.util.HostsFileReader;
import org.apache.hadoop.util.ReflectionUtils;
import org.apache.hadoop.util.StringUtils;
import org.apache.hadoop.util.VersionInfo;

/*******************************************************
 * JobTracker is the central location for submitting and tracking MR jobs in a
 * network environment.
 * 
 *******************************************************/
public class JobTracker implements MRConstants, InterTrackerProtocol,
		JobSubmissionProtocol, TaskTrackerManager,
		RefreshAuthorizationPolicyProtocol {

	static {
		Configuration.addDefaultResource("mapred-default.xml");
		Configuration.addDefaultResource("mapred-site.xml");
	}

	static long TASKTRACKER_EXPIRY_INTERVAL = 10 * 60 * 1000;
	static long RETIRE_JOB_INTERVAL;
	static long RETIRE_JOB_CHECK_INTERVAL;
	// The interval after which one fault of a tracker will be discarded,
	// if there are no faults during this.
	private static long UPDATE_FAULTY_TRACKER_INTERVAL = 24 * 60 * 60 * 1000;
	// The maximum percentage of trackers in cluster added
	// to the 'blacklist' across all the jobs.
	private static double MAX_BLACKLIST_PERCENT = 0.50;
	// A tracker is blacklisted across jobs only if number of
	// blacklists are X% above the average number of blacklists.
	// X is the blacklist threshold here.
	private double AVERAGE_BLACKLIST_THRESHOLD = 0.50;
	// The maximum number of blacklists for a tracker after which the
	// tracker could be blacklisted across all jobs
	private int MAX_BLACKLISTS_PER_TRACKER = 4;

	public static enum State {
		INITIALIZING, RUNNING
	}

	State state = State.INITIALIZING;
	private static final int FS_ACCESS_RETRY_PERIOD = 10000;

	private DNSToSwitchMapping dnsToSwitchMapping;
	private NetworkTopology clusterMap = new NetworkTopology();
	private int numTaskCacheLevels; // the max level to which we cache tasks
	private Set<Node> nodesAtMaxLevel = new HashSet<Node>();
	private final TaskScheduler taskScheduler;
	private final List<JobInProgressListener> jobInProgressListeners = new CopyOnWriteArrayList<JobInProgressListener>();

	// system directories are world-wide readable and owner readable
	final static FsPermission SYSTEM_DIR_PERMISSION = FsPermission
			.createImmutable((short) 0733); // rwx-wx-wx

	// system files should have 700 permission
	final static FsPermission SYSTEM_FILE_PERMISSION = FsPermission
			.createImmutable((short) 0700); // rwx------

	/**
	 * A client tried to submit a job before the Job Tracker was ready.
	 */
	public static class IllegalStateException extends IOException {
		public IllegalStateException(String msg) {
			super(msg);
		}
	}

	/**
	 * The maximum no. of 'completed' (successful/failed/killed) jobs kept in
	 * memory per-user.
	 */
	final int MAX_COMPLETE_USER_JOBS_IN_MEMORY;

	/**
	 * The minimum time (in ms) that a job's information has to remain in the
	 * JobTracker's memory before it is retired.
	 */
	static final int MIN_TIME_BEFORE_RETIRE = 60000;

	private int nextJobId = 1;

	public static final Log LOG = LogFactory.getLog(JobTracker.class);

	/**
	 * Start the JobTracker with given configuration.
	 * 
	 * The conf will be modified to reflect the actual ports on which the
	 * JobTracker is up and running if the user passes the port as
	 * <code>zero</code>.
	 * 
	 * @param conf
	 *            configuration for the JobTracker.
	 * @throws IOException
	 */
	public static JobTracker startTracker(JobConf conf) throws IOException,
			InterruptedException {
		return startTracker(conf, generateNewIdentifier());
	}

	public static JobTracker startTracker(JobConf conf, String identifier)
			throws IOException, InterruptedException {
		JobTracker result = null;
		while (true) {
			try {
				result = new JobTracker(conf, identifier);
				result.taskScheduler.setTaskTrackerManager(result);
				break;
			} catch (VersionMismatch e) {
				throw e;
			} catch (BindException e) {
				throw e;
			} catch (UnknownHostException e) {
				throw e;
			} catch (AccessControlException ace) {
				// in case of jobtracker not having right access
				// bail out
				throw ace;
			} catch (IOException e) {
				LOG.warn("Error starting tracker: "
						+ StringUtils.stringifyException(e));
			}
			Thread.sleep(1000);
		}
		if (result != null) {
			JobEndNotifier.startNotifier();
		}
		return result;
	}

	public void stopTracker() throws IOException {
		JobEndNotifier.stopNotifier();
		close();
	}

	public long getProtocolVersion(String protocol, long clientVersion)
			throws IOException {
		if (protocol.equals(InterTrackerProtocol.class.getName())) {
			return InterTrackerProtocol.versionID;
		} else if (protocol.equals(JobSubmissionProtocol.class.getName())) {
			return JobSubmissionProtocol.versionID;
		} else if (protocol.equals(RefreshAuthorizationPolicyProtocol.class
				.getName())) {
			return RefreshAuthorizationPolicyProtocol.versionID;
		} else {
			throw new IOException("Unknown protocol to job tracker: "
					+ protocol);
		}
	}

	/**
	 * A thread to timeout tasks that have been assigned to task trackers, but
	 * that haven't reported back yet. Note that I included a stop() method,
	 * even though there is no place where JobTrackers are cleaned up.
	 */
	private class ExpireLaunchingTasks implements Runnable {
		/**
		 * This is a map of the tasks that have been assigned to task trackers,
		 * but that have not yet been seen in a status report. map: task-id ->
		 * time-assigned
		 */
		private Map<TaskAttemptID, Long> launchingTasks = new LinkedHashMap<TaskAttemptID, Long>();

		public void run() {
			while (true) {
				try {
					// Every 3 minutes check for any tasks that are overdue
					Thread.sleep(TASKTRACKER_EXPIRY_INTERVAL / 3);
					long now = System.currentTimeMillis();
					LOG.debug("Starting launching task sweep");
					synchronized (JobTracker.this) {
						synchronized (launchingTasks) {
							Iterator<Map.Entry<TaskAttemptID, Long>> itr = launchingTasks
									.entrySet().iterator();
							while (itr.hasNext()) {
								Map.Entry<TaskAttemptID, Long> pair = itr
										.next();
								TaskAttemptID taskId = pair.getKey();
								long age = now - (pair.getValue()).longValue();
								LOG.info(taskId + " is " + age + " ms debug.");
								if (age > TASKTRACKER_EXPIRY_INTERVAL) {
									LOG.info("Launching task " + taskId
											+ " timed out.");
									TaskInProgress tip = null;
									tip = taskidToTIPMap.get(taskId);
									if (tip != null) {
										JobInProgress job = tip.getJob();
										String trackerName = getAssignedTracker(taskId);
										TaskTrackerStatus trackerStatus = getTaskTracker(trackerName);
										// This might happen when the
										// tasktracker has already
										// expired and this thread tries to call
										// failedtask
										// again. expire tasktracker should have
										// called failed
										// task!
										if (trackerStatus != null)
											job
													.failedTask(
															tip,
															taskId,
															"Error launching task",
															tip.isMapTask() ? TaskStatus.Phase.MAP
																	: TaskStatus.Phase.STARTING,
															TaskStatus.State.FAILED,
															trackerName);
									}
									itr.remove();
								} else {
									// the tasks are sorted by start time, so
									// once we find
									// one that we want to keep, we are done for
									// this cycle.
									break;
								}
							}
						}
					}
				} catch (InterruptedException ie) {
					// all done
					break;
				} catch (Exception e) {
					LOG.error("Expire Launching Task Thread got exception: "
							+ StringUtils.stringifyException(e));
				}
			}
		}

		public void addNewTask(TaskAttemptID taskName) {
			synchronized (launchingTasks) {
				launchingTasks.put(taskName, System.currentTimeMillis());
			}
		}

		public void removeTask(TaskAttemptID taskName) {
			synchronized (launchingTasks) {
				launchingTasks.remove(taskName);
			}
		}
	}

	// /////////////////////////////////////////////////////
	// Used to expire TaskTrackers that have gone down
	// /////////////////////////////////////////////////////
	class ExpireTrackers implements Runnable {
		public ExpireTrackers() {
		}

		/**
		 * The run method lives for the life of the JobTracker, and removes
		 * TaskTrackers that have not checked in for some time.
		 */
		public void run() {
			while (true) {
				try {
					//
					// Thread runs periodically to check whether trackers should
					// be expired.
					// The sleep interval must be no more than half the maximum
					// expiry time
					// for a task tracker.
					//
					Thread.sleep(TASKTRACKER_EXPIRY_INTERVAL / 3);

					//
					// Loop through all expired items in the queue
					//
					// Need to lock the JobTracker here since we are
					// manipulating it's data-structures via
					// ExpireTrackers.run -> JobTracker.lostTaskTracker ->
					// JobInProgress.failedTask ->
					// JobTracker.markCompleteTaskAttempt
					// Also need to lock JobTracker before locking 'taskTracker'
					// &
					// 'trackerExpiryQueue' to prevent deadlock:
					// @see {@link
					// JobTracker.processHeartbeat(TaskTrackerStatus, boolean)}
					synchronized (JobTracker.this) {
						synchronized (taskTrackers) {
							synchronized (trackerExpiryQueue) {
								long now = System.currentTimeMillis();
								TaskTrackerStatus leastRecent = null;
								while ((trackerExpiryQueue.size() > 0)
										&& ((leastRecent = trackerExpiryQueue
												.first()) != null)
										&& (now - leastRecent.getLastSeen() > TASKTRACKER_EXPIRY_INTERVAL)) {

									// Remove profile from head of queue
									trackerExpiryQueue.remove(leastRecent);
									String trackerName = leastRecent
											.getTrackerName();

									// Figure out if last-seen time should be
									// updated, or if tracker is dead
									TaskTrackerStatus newProfile = taskTrackers
											.get(leastRecent.getTrackerName());
									// Items might leave the taskTracker set
									// through other means; the
									// status stored in 'taskTrackers' might be
									// null, which means the
									// tracker has already been destroyed.
									if (newProfile != null) {
										if (now - newProfile.getLastSeen() > TASKTRACKER_EXPIRY_INTERVAL) {
											// Remove completely after marking
											// the tasks as 'KILLED'
											lostTaskTracker(leastRecent
													.getTrackerName());
											// tracker is lost, and if it is
											// blacklisted, remove
											// it from the count of blacklisted
											// trackers in the cluster
											if (isBlacklisted(trackerName)) {
												faultyTrackers.numBlacklistedTrackers -= 1;
											}
											updateTaskTrackerStatus(
													trackerName, null);
										} else {
											// Update time by inserting latest
											// profile
											trackerExpiryQueue.add(newProfile);
										}
									}
								}
							}
						}
					}
				} catch (InterruptedException iex) {
					break;
				} catch (Exception t) {
					LOG.error("Tracker Expiry Thread got exception: "
							+ StringUtils.stringifyException(t));
				}
			}
		}

	}

	// /////////////////////////////////////////////////////
	// Used to remove old finished Jobs that have been around for too long
	// /////////////////////////////////////////////////////
	class RetireJobs implements Runnable {
		public RetireJobs() {
		}

		/**
		 * The run method lives for the life of the JobTracker, and removes Jobs
		 * that are not still running, but which finished a long time ago.
		 */
		public void run() {
			while (true) {
				try {
					Thread.sleep(RETIRE_JOB_CHECK_INTERVAL);
					List<JobInProgress> retiredJobs = new ArrayList<JobInProgress>();
					long now = System.currentTimeMillis();
					long retireBefore = now - RETIRE_JOB_INTERVAL;

					synchronized (jobs) {
						for (JobInProgress job : jobs.values()) {
							if (job.getStatus().getRunState() != JobStatus.RUNNING
									&& job.getStatus().getRunState() != JobStatus.PREP
									&& (job.getFinishTime()
											+ MIN_TIME_BEFORE_RETIRE < now)
									&& (job.getFinishTime() < retireBefore)) {
								retiredJobs.add(job);
							}
						}
					}
					if (!retiredJobs.isEmpty()) {
						synchronized (JobTracker.this) {
							synchronized (jobs) {
								synchronized (taskScheduler) {
									for (JobInProgress job : retiredJobs) {
										removeJobTasks(job);
										jobs
												.remove(job.getProfile()
														.getJobID());
										for (JobInProgressListener l : jobInProgressListeners) {
											l.jobRemoved(job);
										}
										String jobUser = job.getProfile()
												.getUser();
										synchronized (userToJobsMap) {
											ArrayList<JobInProgress> userJobs = userToJobsMap
													.get(jobUser);
											synchronized (userJobs) {
												userJobs.remove(job);
											}
											if (userJobs.isEmpty()) {
												userToJobsMap.remove(jobUser);
											}
										}
										LOG
												.info("Retired job with id: '"
														+ job.getProfile()
																.getJobID()
														+ "' of user '"
														+ jobUser + "'");

										// clean up job files from the local
										// disk
										JobHistory.JobInfo.cleanupJob(job
												.getProfile().getJobID());
									}
								}
							}
						}
					}
				} catch (InterruptedException t) {
					break;
				} catch (Throwable t) {
					LOG.error("Error in retiring job:\n"
							+ StringUtils.stringifyException(t));
				}
			}
		}
	}

	// The FaultInfo which indicates the number of faults of a tracker
	// and when the last fault occurred
	// and whether the tracker is blacklisted across all jobs or not
	private static class FaultInfo {
		int numFaults = 0;
		long lastUpdated;
		boolean blacklisted;

		FaultInfo() {
			numFaults = 0;
			lastUpdated = System.currentTimeMillis();
			blacklisted = false;
		}

		void setFaultCount(int num) {
			numFaults = num;
		}

		void setLastUpdated(long timeStamp) {
			lastUpdated = timeStamp;
		}

		int getFaultCount() {
			return numFaults;
		}

		long getLastUpdated() {
			return lastUpdated;
		}

		boolean isBlacklisted() {
			return blacklisted;
		}

		void setBlacklist(boolean blacklist) {
			blacklisted = blacklist;
		}
	}

	class FaultyTrackersInfo {
		// A map from hostName to its faults
		private Map<String, FaultInfo> potentiallyFaultyTrackers = new HashMap<String, FaultInfo>();
		// This count gives the number of blacklisted trackers in the cluster
		// at any time. This is maintained to avoid iteration over
		// the potentiallyFaultyTrackers to get blacklisted trackers. And also
		// this count doesn't include blacklisted trackers which are lost,
		// although the fault info is maintained for lost trackers.
		private volatile int numBlacklistedTrackers = 0;

		/**
		 * Increments faults(blacklist by job) for the tracker by one.
		 * 
		 * Adds the tracker to the potentially faulty list.
		 * 
		 * @param hostName
		 */
		void incrementFaults(String hostName) {
			synchronized (potentiallyFaultyTrackers) {
				FaultInfo fi = potentiallyFaultyTrackers.get(hostName);
				if (fi == null) {
					fi = new FaultInfo();
					potentiallyFaultyTrackers.put(hostName, fi);
				}
				int numFaults = fi.getFaultCount();
				++numFaults;
				fi.setFaultCount(numFaults);
				fi.setLastUpdated(System.currentTimeMillis());
				if (!fi.isBlacklisted()) {
					if (shouldBlacklist(hostName, numFaults)) {
						LOG.info("Adding " + hostName + " to the blacklist"
								+ " across all jobs");
						removeHostCapacity(hostName);
						fi.setBlacklist(true);
					}
				}
			}
		}

		/**
		 * Blacklists the tracker across all jobs if
		 * <ol>
		 * <li>#faults are more than MAX_BLACKLISTS_PER_TRACKER (configurable)
		 * blacklists</li>
		 * <li>#faults is 50% (configurable) above the average #faults</li>
		 * <li>50% the cluster is not blacklisted yet</li>
		 */
		private boolean shouldBlacklist(String hostName, int numFaults) {
			if (numFaults >= MAX_BLACKLISTS_PER_TRACKER) {
				// calculate avgBlackLists
				long clusterSize = getClusterStatus().getTaskTrackers();
				long sum = 0;
				for (FaultInfo f : potentiallyFaultyTrackers.values()) {
					sum += f.getFaultCount();
				}
				double avg = (double) sum / clusterSize;

				long totalCluster = clusterSize + numBlacklistedTrackers;
				if ((numFaults - avg) > (AVERAGE_BLACKLIST_THRESHOLD * avg)
						&& numBlacklistedTrackers < (totalCluster * MAX_BLACKLIST_PERCENT)) {
					return true;
				}
			}
			return false;
		}

		/**
		 * Removes the tracker from blacklist and from potentially faulty list,
		 * when it is restarted.
		 * 
		 * @param hostName
		 */
		void markTrackerHealthy(String hostName) {
			synchronized (potentiallyFaultyTrackers) {
				FaultInfo fi = potentiallyFaultyTrackers.remove(hostName);
				if (fi != null && fi.isBlacklisted()) {
					LOG.info("Removing " + hostName + " from blacklist");
					addHostCapacity(hostName);
				}
			}
		}

		/**
		 * Check whether tasks can be assigned to the tracker.
		 * 
		 * One fault of the tracker is discarded if there are no faults during
		 * one day. So, the tracker will get a chance again to run tasks of a
		 * job.
		 * 
		 * @param hostName
		 *            The tracker name
		 * @param now
		 *            The current time
		 * 
		 * @return true if the tracker is blacklisted false otherwise
		 */
		boolean shouldAssignTasksToTracker(String hostName, long now) {
			synchronized (potentiallyFaultyTrackers) {
				FaultInfo fi = potentiallyFaultyTrackers.get(hostName);
				if (fi != null
						&& (now - fi.getLastUpdated()) > UPDATE_FAULTY_TRACKER_INTERVAL) {
					int numFaults = fi.getFaultCount() - 1;
					if (fi.isBlacklisted()) {
						LOG.info("Removing " + hostName + " from blacklist");
						addHostCapacity(hostName);
						fi.setBlacklist(false);
					}
					if (numFaults > 0) {
						fi.setFaultCount(numFaults);
						fi.setLastUpdated(now);
					} else {
						potentiallyFaultyTrackers.remove(hostName);
					}
				}
				return (fi != null && fi.isBlacklisted());
			}
		}

		private void removeHostCapacity(String hostName) {
			synchronized (taskTrackers) {
				// remove the capacity of trackers on this host
				for (TaskTrackerStatus status : getStatusesOnHost(hostName)) {
					totalMapTaskCapacity -= status.getMaxMapTasks();
					totalReduceTaskCapacity -= status.getMaxReduceTasks();
				}
				numBlacklistedTrackers += uniqueHostsMap.remove(hostName);
			}
		}

		// This is called on tracker's restart or after a day of blacklist.
		private void addHostCapacity(String hostName) {
			synchronized (taskTrackers) {
				int numTrackersOnHost = 0;
				// add the capacity of trackers on the host
				for (TaskTrackerStatus status : getStatusesOnHost(hostName)) {
					totalMapTaskCapacity += status.getMaxMapTasks();
					totalReduceTaskCapacity += status.getMaxReduceTasks();
					numTrackersOnHost++;
				}
				uniqueHostsMap.put(hostName, numTrackersOnHost);
				numBlacklistedTrackers -= numTrackersOnHost;
			}
		}

		/**
		 * Whether a host is blacklisted across all the jobs.
		 * 
		 * @param hostName
		 * @return
		 */
		boolean isBlacklisted(String hostName) {
			synchronized (potentiallyFaultyTrackers) {
				FaultInfo fi = null;
				if ((fi = potentiallyFaultyTrackers.get(hostName)) != null) {
					return fi.isBlacklisted();
				}
			}
			return false;
		}

		int getFaultCount(String hostName) {
			synchronized (potentiallyFaultyTrackers) {
				FaultInfo fi = null;
				if ((fi = potentiallyFaultyTrackers.get(hostName)) != null) {
					return fi.getFaultCount();
				}
			}
			return 0;
		}
	}

	/**
	 * Get all task tracker statuses on given host
	 * 
	 * @param hostName
	 * @return {@link java.util.List} of {@link TaskTrackerStatus}
	 */
	private List<TaskTrackerStatus> getStatusesOnHost(String hostName) {
		List<TaskTrackerStatus> statuses = new ArrayList<TaskTrackerStatus>();
		synchronized (taskTrackers) {
			for (TaskTrackerStatus status : taskTrackers.values()) {
				if (hostName.equals(status.getHost())) {
					statuses.add(status);
				}
			}
		}
		return statuses;
	}

	// /////////////////////////////////////////////////////
	// Used to recover the jobs upon restart
	// /////////////////////////////////////////////////////
	class RecoveryManager {
		Set<JobID> jobsToRecover; // set of jobs to be recovered

		private int totalEventsRecovered = 0;
		private int restartCount = 0;
		private boolean shouldRecover = false;

		Set<String> recoveredTrackers = Collections
				.synchronizedSet(new HashSet<String>());

		/**
		 * A custom listener that replays the events in the order in which the
		 * events (task attempts) occurred.
		 */
		class JobRecoveryListener implements Listener {
			// The owner job
			private JobInProgress jip;

			private JobHistory.JobInfo job; // current job's info object

			// Maintain the count of the (attempt) events recovered
			private int numEventsRecovered = 0;

			// Maintains open transactions
			private Map<String, String> hangingAttempts = new HashMap<String, String>();

			// Whether there are any updates for this job
			private boolean hasUpdates = false;

			public JobRecoveryListener(JobInProgress jip) {
				this.jip = jip;
				this.job = new JobHistory.JobInfo(jip.getJobID().toString());
			}

			/**
			 * Process a task. Note that a task might commit a previously
			 * pending transaction.
			 */
			private void processTask(String taskId, JobHistory.Task task) {
				// Any TASK info commits the previous transaction
				boolean hasHanging = hangingAttempts.remove(taskId) != null;
				if (hasHanging) {
					numEventsRecovered += 2;
				}

				TaskID id = TaskID.forName(taskId);
				TaskInProgress tip = getTip(id);

				updateTip(tip, task);
			}

			/**
			 * Adds a task-attempt in the listener
			 */
			private void processTaskAttempt(String taskAttemptId,
					JobHistory.TaskAttempt attempt) {
				TaskAttemptID id = TaskAttemptID.forName(taskAttemptId);

				// Check if the transaction for this attempt can be committed
				String taskStatus = attempt.get(Keys.TASK_STATUS);

				if (taskStatus.length() > 0) {
					// This means this is an update event
					if (taskStatus.equals(Values.SUCCESS.name())) {
						// Mark this attempt as hanging
						hangingAttempts.put(id.getTaskID().toString(),
								taskAttemptId);
						addSuccessfulAttempt(jip, id, attempt);
					} else {
						addUnsuccessfulAttempt(jip, id, attempt);
						numEventsRecovered += 2;
					}
				} else {
					createTaskAttempt(jip, id, attempt);
				}
			}

			public void handle(JobHistory.RecordTypes recType,
					Map<Keys, String> values) throws IOException {
				if (recType == JobHistory.RecordTypes.Job) {
					// Update the meta-level job information
					job.handle(values);

					// Forcefully init the job as we have some updates for it
					checkAndInit();
				} else if (recType.equals(JobHistory.RecordTypes.Task)) {
					String taskId = values.get(Keys.TASKID);

					// Create a task
					JobHistory.Task task = new JobHistory.Task();
					task.handle(values);

					// Ignore if its a cleanup task
					if (isCleanup(task)) {
						return;
					}

					// Process the task i.e update the tip state
					processTask(taskId, task);
				} else if (recType.equals(JobHistory.RecordTypes.MapAttempt)) {
					String attemptId = values.get(Keys.TASK_ATTEMPT_ID);

					// Create a task attempt
					JobHistory.MapAttempt attempt = new JobHistory.MapAttempt();
					attempt.handle(values);

					// Ignore if its a cleanup task
					if (isCleanup(attempt)) {
						return;
					}

					// Process the attempt i.e update the attempt state via job
					processTaskAttempt(attemptId, attempt);
				} else if (recType.equals(JobHistory.RecordTypes.ReduceAttempt)) {
					String attemptId = values.get(Keys.TASK_ATTEMPT_ID);

					// Create a task attempt
					JobHistory.ReduceAttempt attempt = new JobHistory.ReduceAttempt();
					attempt.handle(values);

					// Ignore if its a cleanup task
					if (isCleanup(attempt)) {
						return;
					}

					// Process the attempt i.e update the job state via job
					processTaskAttempt(attemptId, attempt);
				}
			}

			// Check if the task is of type CLEANUP
			private boolean isCleanup(JobHistory.Task task) {
				String taskType = task.get(Keys.TASK_TYPE);
				return Values.CLEANUP.name().equals(taskType);
			}

			// Init the job if its ready for init. Also make sure that the
			// scheduler
			// is updated
			private void checkAndInit() throws IOException {
				String jobStatus = this.job.get(Keys.JOB_STATUS);
				if (Values.PREP.name().equals(jobStatus)) {
					hasUpdates = true;
					LOG.info("Calling init from RM for job "
							+ jip.getJobID().toString());
					try {
						initJob(jip);
					} catch (Throwable t) {
						LOG.error("Job initialization failed : \n"
								+ StringUtils.stringifyException(t));
						failJob(jip);
						throw new IOException(t);
					}
				}
			}

			void close() {
				if (hasUpdates) {
					// Apply the final (job-level) updates
					JobStatusChangeEvent event = updateJob(jip, job);

					synchronized (JobTracker.this) {
						// Update the job listeners
						updateJobInProgressListeners(event);
					}
				}
			}

			public int getNumEventsRecovered() {
				return numEventsRecovered;
			}

		}

		public RecoveryManager() {
			jobsToRecover = new TreeSet<JobID>();
		}

		public boolean contains(JobID id) {
			return jobsToRecover.contains(id);
		}

		void addJobForRecovery(JobID id) {
			jobsToRecover.add(id);
		}

		public boolean shouldRecover() {
			return shouldRecover;
		}

		public boolean shouldSchedule() {
			return recoveredTrackers.isEmpty();
		}

		private void markTracker(String trackerName) {
			recoveredTrackers.add(trackerName);
		}

		void unMarkTracker(String trackerName) {
			recoveredTrackers.remove(trackerName);
		}

		Set<JobID> getJobsToRecover() {
			return jobsToRecover;
		}

		/**
		 * Check if the given string represents a job-id or not
		 */
		private boolean isJobNameValid(String str) {
			if (str == null) {
				return false;
			}
			String[] parts = str.split("_");
			if (parts.length == 3) {
				if (parts[0].equals("job")) {
					// other 2 parts should be parseable
					return JobTracker.validateIdentifier(parts[1])
							&& JobTracker.validateJobNumber(parts[2]);
				}
			}
			return false;
		}

		// checks if the job dir has the required files
		public void checkAndAddJob(FileStatus status) throws IOException {
			String fileName = status.getPath().getName();
			if (isJobNameValid(fileName)) {
				if (JobClient.isJobDirValid(status.getPath(), fs)) {
					recoveryManager.addJobForRecovery(JobID.forName(fileName));
					shouldRecover = true; // enable actual recovery if num-files
											// > 1
				} else {
					LOG.info("Found an incomplete job directory " + fileName
							+ "." + " Deleting it!!");
					fs.delete(status.getPath(), true);
				}
			}
		}

		private JobStatusChangeEvent updateJob(JobInProgress jip,
				JobHistory.JobInfo job) {
			// Change the job priority
			String jobpriority = job.get(Keys.JOB_PRIORITY);
			JobPriority priority = JobPriority.valueOf(jobpriority);
			// It's important to update this via the jobtracker's api as it will
			// take care of updating the event listeners too
			setJobPriority(jip.getJobID(), priority);

			// Save the previous job status
			JobStatus oldStatus = (JobStatus) jip.getStatus().clone();

			// Set the start/launch time only if there are recovered tasks
			// Increment the job's restart count
			jip.updateJobInfo(job.getLong(JobHistory.Keys.SUBMIT_TIME), job
					.getLong(JobHistory.Keys.LAUNCH_TIME));

			// Save the new job status
			JobStatus newStatus = (JobStatus) jip.getStatus().clone();

			return new JobStatusChangeEvent(jip, EventType.START_TIME_CHANGED,
					oldStatus, newStatus);
		}

		private void updateTip(TaskInProgress tip, JobHistory.Task task) {
			long startTime = task.getLong(Keys.START_TIME);
			if (startTime != 0) {
				tip.setExecStartTime(startTime);
			}

			long finishTime = task.getLong(Keys.FINISH_TIME);
			// For failed tasks finish-time will be missing
			if (finishTime != 0) {
				tip.setExecFinishTime(finishTime);
			}

			String cause = task.get(Keys.TASK_ATTEMPT_ID);
			if (cause.length() > 0) {
				// This means that the this is a FAILED events
				TaskAttemptID id = TaskAttemptID.forName(cause);
				TaskStatus status = tip.getTaskStatus(id);
				synchronized (JobTracker.this) {
					// This will add the tip failed event in the new log
					tip.getJob().failedTask(tip, id,
							status.getDiagnosticInfo(), status.getPhase(),
							status.getRunState(), status.getTaskTracker());
				}
			}
		}

		private void createTaskAttempt(JobInProgress job,
				TaskAttemptID attemptId, JobHistory.TaskAttempt attempt) {
			TaskID id = attemptId.getTaskID();
			String type = attempt.get(Keys.TASK_TYPE);
			TaskInProgress tip = job.getTaskInProgress(id);

			// I. Get the required info
			TaskStatus taskStatus = null;
			String trackerName = attempt.get(Keys.TRACKER_NAME);
			String trackerHostName = JobInProgress
					.convertTrackerNameToHostName(trackerName);
			// recover the port information.
			int port = 0; // default to 0
			String hport = attempt.get(Keys.HTTP_PORT);
			if (hport != null && hport.length() > 0) {
				port = attempt.getInt(Keys.HTTP_PORT);
			}

			long attemptStartTime = attempt.getLong(Keys.START_TIME);

			// II. Create the (appropriate) task status
			if (type.equals(Values.MAP.name())) {
				taskStatus = new MapTaskStatus(attemptId, 0.0f,
						TaskStatus.State.RUNNING, "", "", trackerName,
						TaskStatus.Phase.MAP, new Counters());
			} else {
				taskStatus = new ReduceTaskStatus(attemptId, 0.0f,
						TaskStatus.State.RUNNING, "", "", trackerName,
						TaskStatus.Phase.REDUCE, new Counters());
			}

			// Set the start time
			taskStatus.setStartTime(attemptStartTime);

			List<TaskStatus> ttStatusList = new ArrayList<TaskStatus>();
			ttStatusList.add(taskStatus);

			// III. Create the dummy tasktracker status
			TaskTrackerStatus ttStatus = new TaskTrackerStatus(trackerName,
					trackerHostName, port, ttStatusList, 0, 0, 0);
			ttStatus.setLastSeen(System.currentTimeMillis());

			synchronized (JobTracker.this) {
				synchronized (taskTrackers) {
					synchronized (trackerExpiryQueue) {
						// IV. Register a new tracker
						boolean isTrackerRegistered = getTaskTracker(trackerName) != null;
						if (!isTrackerRegistered) {
							markTracker(trackerName); // add the tracker to
														// recovery-manager
							addNewTracker(ttStatus);
						}

						// V. Update the tracker status
						// This will update the meta info of the jobtracker and
						// also add the
						// tracker status if missing i.e register it
						updateTaskTrackerStatus(trackerName, ttStatus);
					}
				}
				// Register the attempt with job and tip, under JobTracker lock.
				// Since, as of today they are atomic through heartbeat.
				// VI. Register the attempt
				// a) In the job
				job.addRunningTaskToTIP(tip, attemptId, ttStatus, false);
				// b) In the tip
				tip.updateStatus(taskStatus);
			}

			// VII. Make an entry in the launched tasks
			expireLaunchingTasks.addNewTask(attemptId);
		}

		private void addSuccessfulAttempt(JobInProgress job,
				TaskAttemptID attemptId, JobHistory.TaskAttempt attempt) {
			// I. Get the required info
			TaskID taskId = attemptId.getTaskID();
			String type = attempt.get(Keys.TASK_TYPE);

			TaskInProgress tip = job.getTaskInProgress(taskId);
			long attemptFinishTime = attempt.getLong(Keys.FINISH_TIME);

			// Get the task status and the tracker name and make a copy of it
			TaskStatus taskStatus = (TaskStatus) tip.getTaskStatus(attemptId)
					.clone();
			taskStatus.setFinishTime(attemptFinishTime);

			String stateString = attempt.get(Keys.STATE_STRING);

			// Update the basic values
			taskStatus.setStateString(stateString);
			taskStatus.setProgress(1.0f);
			taskStatus.setRunState(TaskStatus.State.SUCCEEDED);

			// Set the shuffle/sort finished times
			if (type.equals(Values.REDUCE.name())) {
				long shuffleTime = Long.parseLong(attempt
						.get(Keys.SHUFFLE_FINISHED));
				long sortTime = Long.parseLong(attempt.get(Keys.SORT_FINISHED));
				taskStatus.setShuffleFinishTime(shuffleTime);
				taskStatus.setSortFinishTime(sortTime);
			}

			// Add the counters
			String counterString = attempt.get(Keys.COUNTERS);
			Counters counter = null;
			// TODO Check if an exception should be thrown
			try {
				counter = Counters.fromEscapedCompactString(counterString);
			} catch (ParseException pe) {
				counter = new Counters(); // Set it to empty counter
			}
			taskStatus.setCounters(counter);

			synchronized (JobTracker.this) {
				// II. Replay the status
				job.updateTaskStatus(tip, taskStatus);
			}

			// III. Prevent the task from expiry
			expireLaunchingTasks.removeTask(attemptId);
		}

		private void addUnsuccessfulAttempt(JobInProgress job,
				TaskAttemptID attemptId, JobHistory.TaskAttempt attempt) {
			// I. Get the required info
			TaskID taskId = attemptId.getTaskID();
			TaskInProgress tip = job.getTaskInProgress(taskId);
			long attemptFinishTime = attempt.getLong(Keys.FINISH_TIME);

			TaskStatus taskStatus = (TaskStatus) tip.getTaskStatus(attemptId)
					.clone();
			taskStatus.setFinishTime(attemptFinishTime);

			// Reset the progress
			taskStatus.setProgress(0.0f);

			String stateString = attempt.get(Keys.STATE_STRING);
			taskStatus.setStateString(stateString);

			boolean hasFailed = attempt.get(Keys.TASK_STATUS).equals(
					Values.FAILED.name());
			// Set the state failed/killed
			if (hasFailed) {
				taskStatus.setRunState(TaskStatus.State.FAILED);
			} else {
				taskStatus.setRunState(TaskStatus.State.KILLED);
			}

			// Get/Set the error msg
			String diagInfo = attempt.get(Keys.ERROR);
			taskStatus.setDiagnosticInfo(diagInfo); // diag info

			synchronized (JobTracker.this) {
				// II. Update the task status
				job.updateTaskStatus(tip, taskStatus);
			}

			// III. Prevent the task from expiry
			expireLaunchingTasks.removeTask(attemptId);
		}

		Path getRestartCountFile() {
			return new Path(getSystemDir(), "jobtracker.info");
		}

		Path getTempRestartCountFile() {
			return new Path(getSystemDir(), "jobtracker.info.recover");
		}

		/**
		 * Initialize the recovery process. It simply creates a jobtracker.info
		 * file in the jobtracker's system directory and writes its restart
		 * count in it. For the first start, the jobtracker writes '0' in it.
		 * Upon subsequent restarts the jobtracker replaces the count with its
		 * current count which is (old count + 1). The whole purpose of this api
		 * is to obtain restart counts across restarts to avoid attempt-id
		 * clashes.
		 * 
		 * Note that in between if the jobtracker.info files goes missing then
		 * the jobtracker will disable recovery and continue.
		 * 
		 */
		void updateRestartCount() throws IOException {
			Path restartFile = getRestartCountFile();
			Path tmpRestartFile = getTempRestartCountFile();
			FileSystem fs = restartFile.getFileSystem(conf);
			FsPermission filePerm = new FsPermission(SYSTEM_FILE_PERMISSION);

			// read the count from the jobtracker info file
			if (fs.exists(restartFile)) {
				fs.delete(tmpRestartFile, false); // delete the tmp file
			} else if (fs.exists(tmpRestartFile)) {
				// if .rec exists then delete the main file and rename the .rec
				// to main
				fs.rename(tmpRestartFile, restartFile); // rename .rec to main
														// file
			} else {
				// For the very first time the jobtracker will create a
				// jobtracker.info
				// file. If the jobtracker has restarted then disable recovery
				// as files'
				// needed for recovery are missing.

				// disable recovery if this is a restart
				shouldRecover = false;

				// write the jobtracker.info file
				try {
					FSDataOutputStream out = FileSystem.create(fs, restartFile,
							filePerm);
					out.writeInt(0);
					out.close();
				} catch (IOException ioe) {
					LOG.warn("Writing to file " + restartFile + " failed!");
					LOG.warn("FileSystem is not ready yet!");
					fs.delete(restartFile, false);
					throw ioe;
				}
				return;
			}

			FSDataInputStream in = fs.open(restartFile);
			try {
				// read the old count
				restartCount = in.readInt();
				++restartCount; // increment the restart count
			} catch (IOException ioe) {
				LOG.warn("System directory is garbled. Failed to read file "
						+ restartFile);
				LOG
						.warn("Jobtracker recovery is not possible with garbled"
								+ " system directory! Please delete the system directory and"
								+ " restart the jobtracker. Note that deleting the system"
								+ " directory will result in loss of all the running jobs.");
				throw new RuntimeException(ioe);
			} finally {
				if (in != null) {
					in.close();
				}
			}

			// Write back the new restart count and rename the old info file
			// TODO This is similar to jobhistory recovery, maybe this common
			// code
			// can be factored out.

			// write to the tmp file
			FSDataOutputStream out = FileSystem.create(fs, tmpRestartFile,
					filePerm);
			out.writeInt(restartCount);
			out.close();

			// delete the main file
			fs.delete(restartFile, false);

			// rename the .rec to main file
			fs.rename(tmpRestartFile, restartFile);
		}

		public void recover() {
			if (!shouldRecover()) {
				// clean up jobs structure
				jobsToRecover.clear();
				return;
			}

			LOG.info("Restart count of the jobtracker : " + restartCount);

			// I. Init the jobs and cache the recovered job history filenames
			Map<JobID, Path> jobHistoryFilenameMap = new HashMap<JobID, Path>();
			Iterator<JobID> idIter = jobsToRecover.iterator();
			while (idIter.hasNext()) {
				JobID id = idIter.next();
				LOG.info("Trying to recover details of job " + id);
				try {
					// 1. Create the job object
					JobInProgress job = new JobInProgress(id, JobTracker.this,
							conf, restartCount);

					// 2. Check if the user has appropriate access
					// Get the user group info for the job's owner
					UserGroupInformation ugi = UserGroupInformation
							.readFrom(job.getJobConf());
					LOG.info("Submitting job " + id + " on behalf of user "
							+ ugi.getUserName() + " in groups : "
							+ StringUtils.arrayToString(ugi.getGroupNames()));

					// check the access
					try {
						checkAccess(job,
								QueueManager.QueueOperation.SUBMIT_JOB, ugi);
					} catch (Throwable t) {
						LOG.warn("Access denied for user "
								+ ugi.getUserName()
								+ " in groups : ["
								+ StringUtils
										.arrayToString(ugi.getGroupNames())
								+ "]");
						throw t;
					}

					// 3. Get the log file and the file path
					String logFileName = JobHistory.JobInfo
							.getJobHistoryFileName(job.getJobConf(), id);
					if (logFileName != null) {
						Path jobHistoryFilePath = JobHistory.JobInfo
								.getJobHistoryLogLocation(logFileName);

						// 4. Recover the history file. This involved
						// - deleting file.recover if file exists
						// - renaming file.recover to file if file doesnt exist
						// This makes sure that the (master) file exists
						JobHistory.JobInfo.recoverJobHistoryFile(job
								.getJobConf(), jobHistoryFilePath);

						// 5. Cache the history file name as it costs one dfs
						// access
						jobHistoryFilenameMap.put(job.getJobID(),
								jobHistoryFilePath);
					} else {
						LOG.info("No history file found for job " + id);
						idIter.remove(); // remove from recovery list
					}

					// 6. Sumbit the job to the jobtracker
					addJob(id, job);
				} catch (Throwable t) {
					LOG.warn("Failed to recover job " + id
							+ " Ignoring the job.", t);
					idIter.remove();
					continue;
				}
			}

			long recoveryStartTime = System.currentTimeMillis();

			// II. Recover each job
			idIter = jobsToRecover.iterator();
			while (idIter.hasNext()) {
				JobID id = idIter.next();
				JobInProgress pJob = getJob(id);

				// 1. Get the required info
				// Get the recovered history file
				Path jobHistoryFilePath = jobHistoryFilenameMap.get(pJob
						.getJobID());
				String logFileName = jobHistoryFilePath.getName();

				FileSystem fs;
				try {
					fs = jobHistoryFilePath.getFileSystem(conf);
				} catch (IOException ioe) {
					LOG.warn("Failed to get the filesystem for job " + id
							+ ". Ignoring.", ioe);
					continue;
				}

				// 2. Parse the history file
				// Note that this also involves job update
				JobRecoveryListener listener = new JobRecoveryListener(pJob);
				try {
					JobHistory.parseHistoryFromFS(
							jobHistoryFilePath.toString(), listener, fs);
				} catch (Throwable t) {
					LOG.info("Error reading history file of job "
							+ pJob.getJobID()
							+ ". Ignoring the error and continuing.", t);
				}

				// 3. Close the listener
				listener.close();

				// 4. Update the recovery metric
				totalEventsRecovered += listener.getNumEventsRecovered();

				// 5. Cleanup history
				// Delete the master log file as an indication that the new file
				// should be used in future
				try {
					synchronized (pJob) {
						JobHistory.JobInfo.checkpointRecovery(logFileName, pJob
								.getJobConf());
					}
				} catch (Throwable t) {
					LOG.warn("Failed to delete log file (" + logFileName
							+ ") for job " + id + ". Continuing.", t);
				}

				if (pJob.isComplete()) {
					idIter.remove(); // no need to keep this job info as its
										// successful
				}
			}

			recoveryDuration = System.currentTimeMillis() - recoveryStartTime;
			hasRecovered = true;

			// III. Finalize the recovery
			synchronized (trackerExpiryQueue) {
				// Make sure that the tracker statuses in the expiry-tracker
				// queue
				// are updated
				long now = System.currentTimeMillis();
				int size = trackerExpiryQueue.size();
				for (int i = 0; i < size; ++i) {
					// Get the first status
					TaskTrackerStatus status = trackerExpiryQueue.first();

					// Remove it
					trackerExpiryQueue.remove(status);

					// Set the new time
					status.setLastSeen(now);

					// Add back to get the sorted list
					trackerExpiryQueue.add(status);
				}
			}

			LOG.info("Restoration complete");
		}

		int totalEventsRecovered() {
			return totalEventsRecovered;
		}
	}

	private final JobTrackerInstrumentation myInstrumentation;

	// ///////////////////////////////////////////////////////////////
	// The real JobTracker
	// //////////////////////////////////////////////////////////////
	int port;
	String localMachine;
	private String trackerIdentifier;
	long startTime;
	int totalSubmissions = 0;
	private int totalMapTaskCapacity;
	private int totalReduceTaskCapacity;
	private HostsFileReader hostsReader;

	// JobTracker recovery variables
	private volatile boolean hasRestarted = false;
	private volatile boolean hasRecovered = false;
	private volatile long recoveryDuration;

	//
	// Properties to maintain while running Jobs and Tasks:
	//
	// 1. Each Task is always contained in a single Job. A Job succeeds when all
	// its
	// Tasks are complete.
	//
	// 2. Every running or successful Task is assigned to a Tracker. Idle Tasks
	// are not.
	//
	// 3. When a Tracker fails, all of its assigned Tasks are marked as
	// failures.
	//
	// 4. A Task might need to be reexecuted if it (or the machine it's hosted
	// on) fails
	// before the Job is 100% complete. Sometimes an upstream Task can fail
	// without
	// reexecution if all downstream Tasks that require its output have already
	// obtained
	// the necessary files.
	//

	// All the known jobs. (jobid->JobInProgress)
	Map<JobID, JobInProgress> jobs = new TreeMap<JobID, JobInProgress>();

	// (user -> list of JobInProgress)
	TreeMap<String, ArrayList<JobInProgress>> userToJobsMap = new TreeMap<String, ArrayList<JobInProgress>>();

	// (trackerID --> list of jobs to cleanup)
	Map<String, Set<JobID>> trackerToJobsToCleanup = new HashMap<String, Set<JobID>>();

	// (trackerID --> list of tasks to cleanup)
	Map<String, Set<TaskAttemptID>> trackerToTasksToCleanup = new HashMap<String, Set<TaskAttemptID>>();

	// All the known TaskInProgress items, mapped to by taskids (taskid->TIP)
	Map<TaskAttemptID, TaskInProgress> taskidToTIPMap = new TreeMap<TaskAttemptID, TaskInProgress>();

	// (taskid --> trackerID)
	TreeMap<TaskAttemptID, String> taskidToTrackerMap = new TreeMap<TaskAttemptID, String>();

	// (trackerID->TreeSet of taskids running at that tracker)
	TreeMap<String, Set<TaskAttemptID>> trackerToTaskMap = new TreeMap<String, Set<TaskAttemptID>>();

	// (trackerID -> TreeSet of completed taskids running at that tracker)
	TreeMap<String, Set<TaskAttemptID>> trackerToMarkedTasksMap = new TreeMap<String, Set<TaskAttemptID>>();

	// (trackerID --> last sent HeartBeatResponse)
	Map<String, HeartbeatResponse> trackerToHeartbeatResponseMap = new TreeMap<String, HeartbeatResponse>();

	// (hostname --> Node (NetworkTopology))
	Map<String, Node> hostnameToNodeMap = Collections
			.synchronizedMap(new TreeMap<String, Node>());

	// Number of resolved entries
	int numResolved;

	private FaultyTrackersInfo faultyTrackers = new FaultyTrackersInfo();

	//
	// Watch and expire TaskTracker objects using these structures.
	// We can map from Name->TaskTrackerStatus, or we can expire by time.
	//
	int totalMaps = 0;
	int totalReduces = 0;
	private HashMap<String, TaskTrackerStatus> taskTrackers = new HashMap<String, TaskTrackerStatus>();
	Map<String, Integer> uniqueHostsMap = new ConcurrentHashMap<String, Integer>();
	ExpireTrackers expireTrackers = new ExpireTrackers();
	Thread expireTrackersThread = null;
	RetireJobs retireJobs = new RetireJobs();
	Thread retireJobsThread = null;
	ExpireLaunchingTasks expireLaunchingTasks = new ExpireLaunchingTasks();
	Thread expireLaunchingTaskThread = new Thread(expireLaunchingTasks,
			"expireLaunchingTasks");

	CompletedJobStatusStore completedJobStatusStore = null;
	Thread completedJobsStoreThread = null;
	RecoveryManager recoveryManager;

	/**
	 * It might seem like a bug to maintain a TreeSet of status objects, which
	 * can be updated at any time. But that's not what happens! We only update
	 * status objects in the taskTrackers table. Status objects are never
	 * updated once they enter the expiry queue. Instead, we wait for them to
	 * expire and remove them from the expiry queue. If a status object has been
	 * updated in the taskTracker table, the latest status is reinserted.
	 * Otherwise, we assume the tracker has expired.
	 */
	TreeSet<TaskTrackerStatus> trackerExpiryQueue = new TreeSet<TaskTrackerStatus>(
			new Comparator<TaskTrackerStatus>() {
				public int compare(TaskTrackerStatus p1, TaskTrackerStatus p2) {
					if (p1.getLastSeen() < p2.getLastSeen()) {
						return -1;
					} else if (p1.getLastSeen() > p2.getLastSeen()) {
						return 1;
					} else {
						return (p1.getTrackerName().compareTo(p2
								.getTrackerName()));
					}
				}
			});

	// Used to provide an HTML view on Job, Task, and TaskTracker structures
	final HttpServer infoServer;
	int infoPort;

	Server interTrackerServer;

	// Some jobs are stored in a local system directory. We can delete
	// the files when we're done with the job.
	static final String SUBDIR = "jobTracker";
	FileSystem fs = null;
	Path systemDir = null;
	private JobConf conf;

	long limitMaxMemForMapTasks;
	long limitMaxMemForReduceTasks;
	long memSizeForMapSlotOnJT;
	long memSizeForReduceSlotOnJT;

	private QueueManager queueManager;

	/**
	 * Start the JobTracker process, listen on the indicated port
	 */
	JobTracker(JobConf conf) throws IOException, InterruptedException {
		this(conf, generateNewIdentifier());
	}

	JobTracker(JobConf conf, String identifier) throws IOException,
			InterruptedException {
		//
		// Grab some static constants
		//
		TASKTRACKER_EXPIRY_INTERVAL = conf.getLong(
				"mapred.tasktracker.expiry.interval", 10 * 60 * 1000);
		RETIRE_JOB_INTERVAL = conf.getLong(
				"mapred.jobtracker.retirejob.interval", 24 * 60 * 60 * 1000);
		RETIRE_JOB_CHECK_INTERVAL = conf.getLong(
				"mapred.jobtracker.retirejob.check", 60 * 1000);
		MAX_COMPLETE_USER_JOBS_IN_MEMORY = conf.getInt(
				"mapred.jobtracker.completeuserjobs.maximum", 100);
		MAX_BLACKLISTS_PER_TRACKER = conf.getInt(
				"mapred.max.tracker.blacklists", 4);

		// This configuration is there solely for tuning purposes and
		// once this feature has been tested in real clusters and an appropriate
		// value for the threshold has been found, this config might be taken
		// out.
		AVERAGE_BLACKLIST_THRESHOLD = conf.getFloat(
				"mapred.cluster.average.blacklist.threshold", 0.5f);

		// This is a directory of temporary submission files. We delete it
		// on startup, and can delete any files that we're done with
		this.conf = conf;
		JobConf jobConf = new JobConf(conf);

		initializeTaskMemoryRelatedConfig();

		// Read the hosts/exclude files to restrict access to the jobtracker.
		this.hostsReader = new HostsFileReader(conf.get("mapred.hosts", ""),
				conf.get("mapred.hosts.exclude", ""));

		queueManager = new QueueManager(this.conf);

		// Create the scheduler
		Class<? extends TaskScheduler> schedulerClass = conf.getClass(
				"mapred.jobtracker.taskScheduler", JobQueueTaskScheduler.class,
				TaskScheduler.class);
		taskScheduler = (TaskScheduler) ReflectionUtils.newInstance(
				schedulerClass, conf);

		// Set ports, start RPC servers, setup security policy etc.
		InetSocketAddress addr = getAddress(conf);
		this.localMachine = addr.getHostName();
		this.port = addr.getPort();

		// Set service-level authorization security policy
		if (conf
				.getBoolean(
						ServiceAuthorizationManager.SERVICE_AUTHORIZATION_CONFIG,
						false)) {
			PolicyProvider policyProvider = (PolicyProvider) (ReflectionUtils
					.newInstance(conf
							.getClass(PolicyProvider.POLICY_PROVIDER_CONFIG,
									MapReducePolicyProvider.class,
									PolicyProvider.class), conf));
			SecurityUtil.setPolicy(new ConfiguredPolicy(conf, policyProvider));
		}

		int handlerCount = conf.getInt("mapred.job.tracker.handler.count", 10);
		this.interTrackerServer = RPC.getServer(this, addr.getHostName(), addr
				.getPort(), handlerCount, false, conf);
		if (LOG.isDebugEnabled()) {
			Properties p = System.getProperties();
			for (Iterator it = p.keySet().iterator(); it.hasNext();) {
				String key = (String) it.next();
				String val = p.getProperty(key);
				LOG.debug("Property '" + key + "' is " + val);
			}
		}

		String infoAddr = NetUtils.getServerAddress(conf,
				"mapred.job.tracker.info.bindAddress",
				"mapred.job.tracker.info.port",
				"mapred.job.tracker.http.address");
		InetSocketAddress infoSocAddr = NetUtils.createSocketAddr(infoAddr);
		String infoBindAddress = infoSocAddr.getHostName();
		int tmpInfoPort = infoSocAddr.getPort();
		this.startTime = System.currentTimeMillis();
		infoServer = new HttpServer("job", infoBindAddress, tmpInfoPort,
				tmpInfoPort == 0, conf);
		infoServer.setAttribute("job.tracker", this);
		// initialize history parameters.
		boolean historyInitialized = JobHistory.init(conf, this.localMachine,
				this.startTime);
		String historyLogDir = null;
		FileSystem historyFS = null;
		if (historyInitialized) {
			historyLogDir = conf.get("hadoop.job.history.location");
			infoServer.setAttribute("historyLogDir", historyLogDir);
			historyFS = new Path(historyLogDir).getFileSystem(conf);
			infoServer.setAttribute("fileSys", historyFS);
		}
		infoServer.addServlet("reducegraph", "/taskgraph",
				TaskGraphServlet.class);
		infoServer.start();

		this.trackerIdentifier = identifier;

		// Initialize instrumentation
		JobTrackerInstrumentation tmp;
		Class<? extends JobTrackerInstrumentation> metricsInst = getInstrumentationClass(jobConf);
		try {
			java.lang.reflect.Constructor<? extends JobTrackerInstrumentation> c = metricsInst
					.getConstructor(new Class[] { JobTracker.class,
							JobConf.class });
			tmp = c.newInstance(this, jobConf);
		} catch (Exception e) {
			// Reflection can throw lots of exceptions -- handle them all by
			// falling back on the default.
			LOG.error("failed to initialize job tracker metrics", e);
			tmp = new JobTrackerMetricsInst(this, jobConf);
		}
		myInstrumentation = tmp;

		// The rpc/web-server ports can be ephemeral ports...
		// ... ensure we have the correct info
		this.port = interTrackerServer.getListenerAddress().getPort();
		this.conf.set("mapred.job.tracker",
				(this.localMachine + ":" + this.port));
		LOG.info("JobTracker up at: " + this.port);
		this.infoPort = this.infoServer.getPort();
		this.conf.set("mapred.job.tracker.http.address", infoBindAddress + ":"
				+ this.infoPort);
		LOG.info("JobTracker webserver: " + this.infoServer.getPort());

		// start the recovery manager
		recoveryManager = new RecoveryManager();

		while (!Thread.currentThread().isInterrupted()) {
			try {
				// if we haven't contacted the namenode go ahead and do it
				if (fs == null) {
					fs = FileSystem.get(conf);
				}
				// clean up the system dir, which will only work if hdfs is out
				// of
				// safe mode
				if (systemDir == null) {
					systemDir = new Path(getSystemDir());
				}
				// Make sure that the backup data is preserved
				FileStatus[] systemDirData = fs.listStatus(this.systemDir);
				// Check if the history is enabled .. as we cant have
				// persistence with
				// history disabled
				if (conf.getBoolean("mapred.jobtracker.restart.recover", false)
						&& !JobHistory.isDisableHistory()
						&& systemDirData != null) {
					for (FileStatus status : systemDirData) {
						try {
							recoveryManager.checkAndAddJob(status);
						} catch (Throwable t) {
							LOG.warn("Failed to add the job "
									+ status.getPath().getName(), t);
						}
					}

					// Check if there are jobs to be recovered
					hasRestarted = recoveryManager.shouldRecover();
					if (hasRestarted) {
						break; // if there is something to recover else clean
								// the sys dir
					}
				}
				LOG.info("Cleaning up the system directory");
				fs.delete(systemDir, true);
				if (FileSystem.mkdirs(fs, systemDir, new FsPermission(
						SYSTEM_DIR_PERMISSION))) {
					break;
				}
				LOG.error("Mkdirs failed to create " + systemDir);
			} catch (AccessControlException ace) {
				LOG.warn("Failed to operate on mapred.system.dir (" + systemDir
						+ ") because of permissions.");
				LOG.warn("Manually delete the mapred.system.dir (" + systemDir
						+ ") and then start the JobTracker.");
				LOG.warn("Bailing out ... ");
				throw ace;
			} catch (IOException ie) {
				LOG.info("problem cleaning system directory: " + systemDir, ie);
			}
			Thread.sleep(FS_ACCESS_RETRY_PERIOD);
		}

		if (Thread.currentThread().isInterrupted()) {
			throw new InterruptedException();
		}

		// Same with 'localDir' except it's always on the local disk.
		jobConf.deleteLocalFiles(SUBDIR);

		// Initialize history again if it is not initialized
		// because history was on dfs and namenode was in safemode.
		if (!historyInitialized) {
			JobHistory.init(conf, this.localMachine, this.startTime);
			historyLogDir = conf.get("hadoop.job.history.location");
			infoServer.setAttribute("historyLogDir", historyLogDir);
			historyFS = new Path(historyLogDir).getFileSystem(conf);
			infoServer.setAttribute("fileSys", historyFS);
		}

		this.dnsToSwitchMapping = ReflectionUtils.newInstance(conf.getClass(
				"topology.node.switch.mapping.impl", ScriptBasedMapping.class,
				DNSToSwitchMapping.class), conf);
		this.numTaskCacheLevels = conf.getInt("mapred.task.cache.levels",
				NetworkTopology.DEFAULT_HOST_LEVEL);

		// initializes the job status store
		completedJobStatusStore = new CompletedJobStatusStore(conf);
	}

	private static SimpleDateFormat getDateFormat() {
		return new SimpleDateFormat("yyyyMMddHHmm");
	}

	private static String generateNewIdentifier() {
		return getDateFormat().format(new Date());
	}

	static boolean validateIdentifier(String id) {
		try {
			// the jobtracker id should be 'date' parseable
			getDateFormat().parse(id);
			return true;
		} catch (ParseException pe) {
		}
		return false;
	}

	static boolean validateJobNumber(String id) {
		try {
			// the job number should be integer parseable
			Integer.parseInt(id);
			return true;
		} catch (IllegalArgumentException pe) {
		}
		return false;
	}

	/**
	 * Whether the JT has restarted
	 */
	public boolean hasRestarted() {
		return hasRestarted;
	}

	/**
	 * Whether the JT has recovered upon restart
	 */
	public boolean hasRecovered() {
		return hasRecovered;
	}

	/**
	 * How long the jobtracker took to recover from restart.
	 */
	public long getRecoveryDuration() {
		return hasRestarted() ? recoveryDuration : 0;
	}

	public static Class<? extends JobTrackerInstrumentation> getInstrumentationClass(
			Configuration conf) {
		return conf.getClass("mapred.jobtracker.instrumentation",
				JobTrackerMetricsInst.class, JobTrackerInstrumentation.class);
	}

	public static void setInstrumentationClass(Configuration conf,
			Class<? extends JobTrackerInstrumentation> t) {
		conf.setClass("mapred.jobtracker.instrumentation", t,
				JobTrackerInstrumentation.class);
	}

	JobTrackerInstrumentation getInstrumentation() {
		return myInstrumentation;
	}

	public static InetSocketAddress getAddress(Configuration conf) {
		String jobTrackerStr = conf.get("mapred.job.tracker", "localhost:8012");
		return NetUtils.createSocketAddr(jobTrackerStr);
	}

	/**
	 * Run forever
	 */
	public void offerService() throws InterruptedException, IOException {
		// Prepare for recovery. This is done irrespective of the status of
		// restart
		// flag.
		while (true) {
			try {
				recoveryManager.updateRestartCount();
				break;
			} catch (IOException ioe) {
				LOG.warn("Failed to initialize recovery manager. ", ioe);
				// wait for some time
				Thread.sleep(FS_ACCESS_RETRY_PERIOD);
				LOG.warn("Retrying...");
			}
		}

		taskScheduler.start();

		// Start the recovery after starting the scheduler
		try {
			recoveryManager.recover();
		} catch (Throwable t) {
			LOG.warn("Recovery manager crashed! Ignoring.", t);
		}

		this.expireTrackersThread = new Thread(this.expireTrackers,
				"expireTrackers");
		this.expireTrackersThread.start();
		this.retireJobsThread = new Thread(this.retireJobs, "retireJobs");
		this.retireJobsThread.start();
		expireLaunchingTaskThread.start();

		if (completedJobStatusStore.isActive()) {
			completedJobsStoreThread = new Thread(completedJobStatusStore,
					"completedjobsStore-housekeeper");
			completedJobsStoreThread.start();
		}

		// start the inter-tracker server once the jt is ready
		this.interTrackerServer.start();

		synchronized (this) {
			state = State.RUNNING;
		}
		LOG.info("Starting RUNNING");

		this.interTrackerServer.join();
		LOG.info("Stopped interTrackerServer");
	}

	void close() throws IOException {
		if (this.infoServer != null) {
			LOG.info("Stopping infoServer");
			try {
				this.infoServer.stop();
			} catch (Exception ex) {
				LOG.warn("Exception shutting down JobTracker", ex);
			}
		}
		if (this.interTrackerServer != null) {
			LOG.info("Stopping interTrackerServer");
			this.interTrackerServer.stop();
		}
		if (this.expireTrackersThread != null
				&& this.expireTrackersThread.isAlive()) {
			LOG.info("Stopping expireTrackers");
			this.expireTrackersThread.interrupt();
			try {
				this.expireTrackersThread.join();
			} catch (InterruptedException ex) {
				ex.printStackTrace();
			}
		}
		if (this.retireJobsThread != null && this.retireJobsThread.isAlive()) {
			LOG.info("Stopping retirer");
			this.retireJobsThread.interrupt();
			try {
				this.retireJobsThread.join();
			} catch (InterruptedException ex) {
				ex.printStackTrace();
			}
		}
		if (taskScheduler != null) {
			taskScheduler.terminate();
		}
		if (this.expireLaunchingTaskThread != null
				&& this.expireLaunchingTaskThread.isAlive()) {
			LOG.info("Stopping expireLaunchingTasks");
			this.expireLaunchingTaskThread.interrupt();
			try {
				this.expireLaunchingTaskThread.join();
			} catch (InterruptedException ex) {
				ex.printStackTrace();
			}
		}
		if (this.completedJobsStoreThread != null
				&& this.completedJobsStoreThread.isAlive()) {
			LOG.info("Stopping completedJobsStore thread");
			this.completedJobsStoreThread.interrupt();
			try {
				this.completedJobsStoreThread.join();
			} catch (InterruptedException ex) {
				ex.printStackTrace();
			}
		}
		LOG.info("stopped all jobtracker services");
		return;
	}

	// /////////////////////////////////////////////////////
	// Maintain lookup tables; called by JobInProgress
	// and TaskInProgress
	// /////////////////////////////////////////////////////
	void createTaskEntry(TaskAttemptID taskid, String taskTracker,
			TaskInProgress tip) {
		LOG.info("Adding task "
				+ (tip.isCleanupAttempt(taskid) ? "(cleanup)" : "") + "'"
				+ taskid + "' to tip " + tip.getTIPId() + ", for tracker '"
				+ taskTracker + "'");

		// taskid --> tracker
		taskidToTrackerMap.put(taskid, taskTracker);

		// tracker --> taskid
		Set<TaskAttemptID> taskset = trackerToTaskMap.get(taskTracker);
		if (taskset == null) {
			taskset = new TreeSet<TaskAttemptID>();
			trackerToTaskMap.put(taskTracker, taskset);
		}
		taskset.add(taskid);

		// taskid --> TIP
		taskidToTIPMap.put(taskid, tip);

	}

	void removeTaskEntry(TaskAttemptID taskid) {
		// taskid --> tracker
		String tracker = taskidToTrackerMap.remove(taskid);

		// tracker --> taskid
		if (tracker != null) {
			Set<TaskAttemptID> trackerSet = trackerToTaskMap.get(tracker);
			if (trackerSet != null) {
				trackerSet.remove(taskid);
			}
		}

		// taskid --> TIP
		taskidToTIPMap.remove(taskid);

		LOG.debug("Removing task '" + taskid + "'");
	}

	/**
	 * Mark a 'task' for removal later. This function assumes that the
	 * JobTracker is locked on entry.
	 * 
	 * @param taskTracker
	 *            the tasktracker at which the 'task' was running
	 * @param taskid
	 *            completed (success/failure/killed) task
	 */
	void markCompletedTaskAttempt(String taskTracker, TaskAttemptID taskid) {
		// tracker --> taskid
		Set<TaskAttemptID> taskset = trackerToMarkedTasksMap.get(taskTracker);
		if (taskset == null) {
			taskset = new TreeSet<TaskAttemptID>();
			trackerToMarkedTasksMap.put(taskTracker, taskset);
		}
		taskset.add(taskid);

		LOG.debug("Marked '" + taskid + "' from '" + taskTracker + "'");
	}

	/**
	 * Mark all 'non-running' jobs of the job for pruning. This function assumes
	 * that the JobTracker is locked on entry.
	 * 
	 * @param job
	 *            the completed job
	 */
	void markCompletedJob(JobInProgress job) {
		for (TaskInProgress tip : job.getSetupTasks()) {
			for (TaskStatus taskStatus : tip.getTaskStatuses()) {
				if (taskStatus.getRunState() != TaskStatus.State.RUNNING
						&& taskStatus.getRunState() != TaskStatus.State.COMMIT_PENDING
						&& taskStatus.getRunState() != TaskStatus.State.UNASSIGNED) {
					markCompletedTaskAttempt(taskStatus.getTaskTracker(),
							taskStatus.getTaskID());
				}
			}
		}
		for (TaskInProgress tip : job.getMapTasks()) {
			for (TaskStatus taskStatus : tip.getTaskStatuses()) {
				if (taskStatus.getRunState() != TaskStatus.State.RUNNING
						&& taskStatus.getRunState() != TaskStatus.State.COMMIT_PENDING
						&& taskStatus.getRunState() != TaskStatus.State.FAILED_UNCLEAN
						&& taskStatus.getRunState() != TaskStatus.State.KILLED_UNCLEAN
						&& taskStatus.getRunState() != TaskStatus.State.UNASSIGNED) {
					markCompletedTaskAttempt(taskStatus.getTaskTracker(),
							taskStatus.getTaskID());
				}
			}
		}
		for (TaskInProgress tip : job.getReduceTasks()) {
			for (TaskStatus taskStatus : tip.getTaskStatuses()) {
				if (taskStatus.getRunState() != TaskStatus.State.RUNNING
						&& taskStatus.getRunState() != TaskStatus.State.COMMIT_PENDING
						&& taskStatus.getRunState() != TaskStatus.State.FAILED_UNCLEAN
						&& taskStatus.getRunState() != TaskStatus.State.KILLED_UNCLEAN
						&& taskStatus.getRunState() != TaskStatus.State.UNASSIGNED) {
					markCompletedTaskAttempt(taskStatus.getTaskTracker(),
							taskStatus.getTaskID());
				}
			}
		}
	}

	/**
	 * Remove all 'marked' tasks running on a given {@link TaskTracker} from the
	 * {@link JobTracker}'s data-structures. This function assumes that the
	 * JobTracker is locked on entry.
	 * 
	 * @param taskTracker
	 *            tasktracker whose 'non-running' tasks are to be purged
	 */
	private void removeMarkedTasks(String taskTracker) {
		// Purge all the 'marked' tasks which were running at taskTracker
		Set<TaskAttemptID> markedTaskSet = trackerToMarkedTasksMap
				.get(taskTracker);
		if (markedTaskSet != null) {
			for (TaskAttemptID taskid : markedTaskSet) {
				removeTaskEntry(taskid);
				LOG.info("Removed completed task '" + taskid + "' from '"
						+ taskTracker + "'");
			}
			// Clear
			trackerToMarkedTasksMap.remove(taskTracker);
		}
	}

	/**
	 * Call {@link #removeTaskEntry(String)} for each of the job's tasks. When
	 * the JobTracker is retiring the long-completed job, either because it has
	 * outlived {@link #RETIRE_JOB_INTERVAL} or the limit of
	 * {@link #MAX_COMPLETE_USER_JOBS_IN_MEMORY} jobs has been reached, we can
	 * afford to nuke all it's tasks; a little unsafe, but practically feasible.
	 * 
	 * @param job
	 *            the job about to be 'retired'
	 */
	synchronized private void removeJobTasks(JobInProgress job) {
		for (TaskInProgress tip : job.getMapTasks()) {
			for (TaskStatus taskStatus : tip.getTaskStatuses()) {
				removeTaskEntry(taskStatus.getTaskID());
			}
		}
		for (TaskInProgress tip : job.getReduceTasks()) {
			for (TaskStatus taskStatus : tip.getTaskStatuses()) {
				removeTaskEntry(taskStatus.getTaskID());
			}
		}
	}

	/**
	 * Safe clean-up all data structures at the end of the job
	 * (success/failure/killed). Here we also ensure that for a given user we
	 * maintain information for only MAX_COMPLETE_USER_JOBS_IN_MEMORY jobs on
	 * the JobTracker.
	 * 
	 * @param job
	 *            completed job.
	 */
	synchronized void finalizeJob(JobInProgress job) {
		// Mark the 'non-running' tasks for pruning
		markCompletedJob(job);

		JobEndNotifier.registerNotification(job.getJobConf(), job.getStatus());

		// start the merge of log files
		JobID id = job.getStatus().getJobID();
		if (job.hasRestarted()) {
			try {
				JobHistory.JobInfo.finalizeRecovery(id, job.getJobConf());
			} catch (IOException ioe) {
				LOG.info("Failed to finalize the log file recovery for job "
						+ id, ioe);
			}
		}

		final JobTrackerInstrumentation metrics = getInstrumentation();
		metrics.finalizeJob(conf, id);

		long now = System.currentTimeMillis();

		// mark the job for cleanup at all the trackers
		addJobForCleanup(id);

		// add the blacklisted trackers to potentially faulty list
		if (job.getStatus().getRunState() == JobStatus.SUCCEEDED) {
			if (job.getNoOfBlackListedTrackers() > 0) {
				for (String hostName : job.getBlackListedTrackers()) {
					faultyTrackers.incrementFaults(hostName);
				}
			}
		}

		// Purge oldest jobs and keep at-most MAX_COMPLETE_USER_JOBS_IN_MEMORY
		// jobs of a given user
		// in memory; information about the purged jobs is available via
		// JobHistory.
		synchronized (jobs) {
			synchronized (taskScheduler) {
				synchronized (userToJobsMap) {
					String jobUser = job.getProfile().getUser();
					if (!userToJobsMap.containsKey(jobUser)) {
						userToJobsMap.put(jobUser,
								new ArrayList<JobInProgress>());
					}
					ArrayList<JobInProgress> userJobs = userToJobsMap
							.get(jobUser);
					synchronized (userJobs) {
						// Add the currently completed 'job'
						userJobs.add(job);

						// Check if we need to retire some jobs of this user
						while (userJobs.size() > MAX_COMPLETE_USER_JOBS_IN_MEMORY) {
							JobInProgress rjob = userJobs.get(0);

							// Do not delete 'current'
							// finished job just yet.
							if (rjob == job) {
								break;
							}

							// do not retire jobs that finished in the very
							// recent past.
							if (rjob.getFinishTime() + MIN_TIME_BEFORE_RETIRE > now) {
								break;
							}

							// Cleanup all datastructures
							int rjobRunState = rjob.getStatus().getRunState();
							if (rjobRunState == JobStatus.SUCCEEDED
									|| rjobRunState == JobStatus.FAILED
									|| rjobRunState == JobStatus.KILLED) {
								// Ok, this call to removeTaskEntries
								// is dangerous is some very very obscure
								// cases; e.g. when rjob completed, hit
								// MAX_COMPLETE_USER_JOBS_IN_MEMORY job
								// limit and yet some task (taskid)
								// wasn't complete!
								removeJobTasks(rjob);

								userJobs.remove(0);
								jobs.remove(rjob.getProfile().getJobID());
								for (JobInProgressListener listener : jobInProgressListeners) {
									listener.jobRemoved(rjob);
								}

								LOG.info("Retired job with id: '"
										+ rjob.getProfile().getJobID()
										+ "' of user: '" + jobUser + "'");
							} else {
								// Do not remove jobs that aren't complete.
								// Stop here, and let the next pass take
								// care of purging jobs.
								break;
							}
						}
					}
					if (userJobs.isEmpty()) {
						userToJobsMap.remove(jobUser);
					}
				}
			}
		}
	}

	// /////////////////////////////////////////////////////
	// Accessors for objects that want info on jobs, tasks,
	// trackers, etc.
	// /////////////////////////////////////////////////////
	public int getTotalSubmissions() {
		return totalSubmissions;
	}

	public String getJobTrackerMachine() {
		return localMachine;
	}

	/**
	 * Get the unique identifier (ie. timestamp) of this job tracker start.
	 * 
	 * @return a string with a unique identifier
	 */
	public String getTrackerIdentifier() {
		return trackerIdentifier;
	}

	public int getTrackerPort() {
		return port;
	}

	public int getInfoPort() {
		return infoPort;
	}

	public long getStartTime() {
		return startTime;
	}

	public Vector<JobInProgress> runningJobs() {
		Vector<JobInProgress> v = new Vector<JobInProgress>();
		for (Iterator it = jobs.values().iterator(); it.hasNext();) {
			JobInProgress jip = (JobInProgress) it.next();
			JobStatus status = jip.getStatus();
			if (status.getRunState() == JobStatus.RUNNING) {
				v.add(jip);
			}
		}
		return v;
	}

	/**
	 * Version that is called from a timer thread, and therefore needs to be
	 * careful to synchronize.
	 */
	public synchronized List<JobInProgress> getRunningJobs() {
		synchronized (jobs) {
			return runningJobs();
		}
	}

	public Vector<JobInProgress> failedJobs() {
		Vector<JobInProgress> v = new Vector<JobInProgress>();
		for (Iterator it = jobs.values().iterator(); it.hasNext();) {
			JobInProgress jip = (JobInProgress) it.next();
			JobStatus status = jip.getStatus();
			if ((status.getRunState() == JobStatus.FAILED)
					|| (status.getRunState() == JobStatus.KILLED)) {
				v.add(jip);
			}
		}
		return v;
	}

	public Vector<JobInProgress> completedJobs() {
		Vector<JobInProgress> v = new Vector<JobInProgress>();
		for (Iterator it = jobs.values().iterator(); it.hasNext();) {
			JobInProgress jip = (JobInProgress) it.next();
			JobStatus status = jip.getStatus();
			if (status.getRunState() == JobStatus.SUCCEEDED) {
				v.add(jip);
			}
		}
		return v;
	}

	/**
	 * Get all the task trackers in the cluster
	 * 
	 * @return {@link Collection} of {@link TaskTrackerStatus}
	 */
	public Collection<TaskTrackerStatus> taskTrackers() {
		synchronized (taskTrackers) {
			return taskTrackers.values();
		}
	}

	/**
	 * Get the active task tracker statuses in the cluster
	 * 
	 * @return {@link Collection} of active {@link TaskTrackerStatus}
	 */
	public Collection<TaskTrackerStatus> activeTaskTrackers() {
		Collection<TaskTrackerStatus> activeTrackers = new ArrayList<TaskTrackerStatus>();
		synchronized (taskTrackers) {
			for (TaskTrackerStatus status : taskTrackers.values()) {
				if (!faultyTrackers.isBlacklisted(status.getHost())) {
					activeTrackers.add(status);
				}
			}
		}
		return activeTrackers;
	}

	/**
	 * Get the active and blacklisted task tracker names in the cluster. The
	 * first element in the returned list contains the list of active tracker
	 * names. The second element in the returned list contains the list of
	 * blacklisted tracker names.
	 */
	public List<List<String>> taskTrackerNames() {
		List<String> activeTrackers = new ArrayList<String>();
		List<String> blacklistedTrackers = new ArrayList<String>();
		synchronized (taskTrackers) {
			for (TaskTrackerStatus status : taskTrackers.values()) {
				if (!faultyTrackers.isBlacklisted(status.getHost())) {
					activeTrackers.add(status.getTrackerName());
				} else {
					blacklistedTrackers.add(status.getTrackerName());
				}
			}
		}
		List<List<String>> result = new ArrayList<List<String>>(2);
		result.add(activeTrackers);
		result.add(blacklistedTrackers);
		return result;
	}

	/**
	 * Get the blacklisted task tracker statuses in the cluster
	 * 
	 * @return {@link Collection} of blacklisted {@link TaskTrackerStatus}
	 */
	public Collection<TaskTrackerStatus> blacklistedTaskTrackers() {
		Collection<TaskTrackerStatus> blacklistedTrackers = new ArrayList<TaskTrackerStatus>();
		synchronized (taskTrackers) {
			for (TaskTrackerStatus status : taskTrackers.values()) {
				if (faultyTrackers.isBlacklisted(status.getHost())) {
					blacklistedTrackers.add(status);
				}
			}
		}
		return blacklistedTrackers;
	}

	int getFaultCount(String hostName) {
		return faultyTrackers.getFaultCount(hostName);
	}

	/**
	 * Get the number of blacklisted trackers across all the jobs
	 * 
	 * @return
	 */
	int getBlacklistedTrackerCount() {
		return faultyTrackers.numBlacklistedTrackers;
	}

	/**
	 * Whether the tracker is blacklisted or not
	 * 
	 * @param trackerID
	 * 
	 * @return true if blacklisted, false otherwise
	 */
	public boolean isBlacklisted(String trackerID) {
		TaskTrackerStatus status = getTaskTracker(trackerID);
		if (status != null) {
			return faultyTrackers.isBlacklisted(status.getHost());
		}
		return false;
	}
	
	/**
	 * get faulty tracker info
	 * @return
	 */
	public FaultyTrackersInfo getFaultyTrackers() {
		return faultyTrackers;
	}

	public TaskTrackerStatus getTaskTracker(String trackerID) {
		synchronized (taskTrackers) {
			return taskTrackers.get(trackerID);
		}
	}

	/**
	 * Adds a new node to the jobtracker. It involves adding it to the expiry
	 * thread and adding it for resolution
	 * 
	 * Assuming trackerExpiryQueue is locked on entry
	 * 
	 * @param status
	 *            Task Tracker's status
	 */
	private void addNewTracker(TaskTrackerStatus status) {
		trackerExpiryQueue.add(status);
		// Register the tracker if its not registered
		if (getNode(status.getTrackerName()) == null) {
			// Making the network location resolution inline ..
			resolveAndAddToTopology(status.getHost());
		}
	}

	public Node resolveAndAddToTopology(String name) {
		List<String> tmpList = new ArrayList<String>(1);
		tmpList.add(name);
		List<String> rNameList = dnsToSwitchMapping.resolve(tmpList);
		String rName = rNameList.get(0);
		String networkLoc = NodeBase.normalize(rName);
		return addHostToNodeMapping(name, networkLoc);
	}

	private Node addHostToNodeMapping(String host, String networkLoc) {
		Node node;
		if ((node = clusterMap.getNode(networkLoc + "/" + host)) == null) {
			node = new NodeBase(host, networkLoc);
			clusterMap.add(node);
			if (node.getLevel() < getNumTaskCacheLevels()) {
				LOG.fatal("Got a host whose level is: " + node.getLevel() + "."
						+ " Should get at least a level of value: "
						+ getNumTaskCacheLevels());
				try {
					stopTracker();
				} catch (IOException ie) {
					LOG.warn("Exception encountered during shutdown: "
							+ StringUtils.stringifyException(ie));
					System.exit(-1);
				}
			}
			hostnameToNodeMap.put(host, node);
			// Make an entry for the node at the max level in the cache
			nodesAtMaxLevel
					.add(getParentNode(node, getNumTaskCacheLevels() - 1));
		}
		return node;
	}

	/**
	 * Returns a collection of nodes at the max level
	 */
	public Collection<Node> getNodesAtMaxLevel() {
		return nodesAtMaxLevel;
	}

	public static Node getParentNode(Node node, int level) {
		for (int i = 0; i < level; ++i) {
			node = node.getParent();
		}
		return node;
	}

	/**
	 * Return the Node in the network topology that corresponds to the hostname
	 */
	public Node getNode(String name) {
		return hostnameToNodeMap.get(name);
	}

	public int getNumTaskCacheLevels() {
		return numTaskCacheLevels;
	}

	public int getNumResolvedTaskTrackers() {
		return numResolved;
	}

	public int getNumberOfUniqueHosts() {
		return uniqueHostsMap.size();
	}

	public void addJobInProgressListener(JobInProgressListener listener) {
		jobInProgressListeners.add(listener);
	}

	public void removeJobInProgressListener(JobInProgressListener listener) {
		jobInProgressListeners.remove(listener);
	}

	// Update the listeners about the job
	// Assuming JobTracker is locked on entry.
	private void updateJobInProgressListeners(JobChangeEvent event) {
		for (JobInProgressListener listener : jobInProgressListeners) {
			listener.jobUpdated(event);
		}
	}

	/**
	 * Return the {@link QueueManager} associated with the JobTracker.
	 */
	public QueueManager getQueueManager() {
		return queueManager;
	}

	// //////////////////////////////////////////////////
	// InterTrackerProtocol
	// //////////////////////////////////////////////////

	public String getBuildVersion() throws IOException {
		return VersionInfo.getBuildVersion();
	}

	/**
	 * The periodic heartbeat mechanism between the {@link TaskTracker} and the
	 * {@link JobTracker}.
	 * 
	 * The {@link JobTracker} processes the status information sent by the
	 * {@link TaskTracker} and responds with instructions to start/stop tasks or
	 * jobs, and also 'reset' instructions during contingencies.
	 */
	public synchronized HeartbeatResponse heartbeat(TaskTrackerStatus status,
			boolean restarted, boolean initialContact, boolean acceptNewTasks,
			short responseId) throws IOException {
		LOG.debug("Got heartbeat from: " + status.getTrackerName()
				+ " (restarted: " + restarted + " initialContact: "
				+ initialContact + " acceptNewTasks: " + acceptNewTasks + ")"
				+ " with responseId: " + responseId);

		// Make sure heartbeat is from a tasktracker allowed by the jobtracker.
		if (!acceptTaskTracker(status)) {
			throw new DisallowedTaskTrackerException(status);
		}

		// First check if the last heartbeat response got through
		String trackerName = status.getTrackerName();
		long now = System.currentTimeMillis();
		boolean isBlacklisted = false;
		if (restarted) {
			faultyTrackers.markTrackerHealthy(status.getHost());
		} else {
			isBlacklisted = faultyTrackers.shouldAssignTasksToTracker(status
					.getHost(), now);
		}

		HeartbeatResponse prevHeartbeatResponse = trackerToHeartbeatResponseMap
				.get(trackerName);
		boolean addRestartInfo = false;

		if (initialContact != true) {
			// If this isn't the 'initial contact' from the tasktracker,
			// there is something seriously wrong if the JobTracker has
			// no record of the 'previous heartbeat'; if so, ask the
			// tasktracker to re-initialize itself.
			if (prevHeartbeatResponse == null) {
				// This is the first heartbeat from the old tracker to the newly
				// started JobTracker
				if (hasRestarted()) {
					addRestartInfo = true;
					// inform the recovery manager about this tracker joining
					// back
					recoveryManager.unMarkTracker(trackerName);
				} else {
					// Jobtracker might have restarted but no recovery is needed
					// otherwise this code should not be reached
					LOG
							.warn("Serious problem, cannot find record of 'previous' "
									+ "heartbeat for '"
									+ trackerName
									+ "'; reinitializing the tasktracker");
					return new HeartbeatResponse(
							responseId,
							new TaskTrackerAction[] { new ReinitTrackerAction() });
				}

			} else {

				// It is completely safe to not process a 'duplicate' heartbeat
				// from a
				// {@link TaskTracker} since it resends the heartbeat when rpcs
				// are
				// lost see {@link TaskTracker.transmitHeartbeat()};
				// acknowledge it by re-sending the previous response to let the
				// {@link TaskTracker} go forward.
				if (prevHeartbeatResponse.getResponseId() != responseId) {
					LOG.info("Ignoring 'duplicate' heartbeat from '"
							+ trackerName
							+ "'; resending the previous 'lost' response");
					return prevHeartbeatResponse;
				}
			}
		}

		// Process this heartbeat
		short newResponseId = (short) (responseId + 1);
		status.setLastSeen(now);
		if (!processHeartbeat(status, initialContact)) {
			if (prevHeartbeatResponse != null) {
				trackerToHeartbeatResponseMap.remove(trackerName);
			}
			return new HeartbeatResponse(newResponseId,
					new TaskTrackerAction[] { new ReinitTrackerAction() });
		}

		// Initialize the response to be sent for the heartbeat
		HeartbeatResponse response = new HeartbeatResponse(newResponseId, null);
		List<TaskTrackerAction> actions = new ArrayList<TaskTrackerAction>();

		// Check for new tasks to be executed on the tasktracker
		if (recoveryManager.shouldSchedule() && acceptNewTasks
				&& !isBlacklisted) {
			TaskTrackerStatus taskTrackerStatus = getTaskTracker(trackerName);
			if (taskTrackerStatus == null) {
				LOG.warn("Unknown task tracker polling; ignoring: "
						+ trackerName);
			} else {
				List<Task> tasks = getSetupAndCleanupTasks(taskTrackerStatus);
				if (tasks == null) {
					tasks = taskScheduler.assignTasks(taskTrackerStatus);
				}
				if (tasks != null) {
					for (Task task : tasks) {
						expireLaunchingTasks.addNewTask(task.getTaskID());
						LOG.debug(trackerName + " -> LaunchTask: "
								+ task.getTaskID());
						actions.add(new LaunchTaskAction(task));
					}
				}
			}
		}

		// Check for tasks to be killed
		List<TaskTrackerAction> killTasksList = getTasksToKill(trackerName);
		if (killTasksList != null) {
			actions.addAll(killTasksList);
		}

		// Check for jobs to be killed/cleanedup
		List<TaskTrackerAction> killJobsList = getJobsForCleanup(trackerName);
		if (killJobsList != null) {
			actions.addAll(killJobsList);
		}

		// Check for tasks whose outputs can be saved
		List<TaskTrackerAction> commitTasksList = getTasksToSave(status);
		if (commitTasksList != null) {
			actions.addAll(commitTasksList);
		}

		// calculate next heartbeat interval and put in heartbeat response
		int nextInterval = getNextHeartbeatInterval();
		response.setHeartbeatInterval(nextInterval);
		response.setActions(actions.toArray(new TaskTrackerAction[actions
				.size()]));

		// check if the restart info is req
		if (addRestartInfo) {
			response.setRecoveredJobs(recoveryManager.getJobsToRecover());
		}

		// Update the trackerToHeartbeatResponseMap
		trackerToHeartbeatResponseMap.put(trackerName, response);

		// Done processing the hearbeat, now remove 'marked' tasks
		removeMarkedTasks(trackerName);

		return response;
	}

	/**
	 * Calculates next heartbeat interval using cluster size. Heartbeat interval
	 * is incremented 1second for every 50 nodes.
	 * 
	 * @return next heartbeat interval.
	 */
	public int getNextHeartbeatInterval() {
		// get the no of task trackers
		int clusterSize = getClusterStatus().getTaskTrackers();
		int heartbeatInterval = Math.max((int) (1000 * Math
				.ceil((double) clusterSize / CLUSTER_INCREMENT)),
				HEARTBEAT_INTERVAL_MIN);
		return heartbeatInterval;
	}

	/**
	 * Return if the specified tasktracker is in the hosts list, if one was
	 * configured. If none was configured, then this returns true.
	 */
	private boolean inHostsList(TaskTrackerStatus status) {
		Set<String> hostsList = hostsReader.getHosts();
		return (hostsList.isEmpty() || hostsList.contains(status.getHost()));
	}

	/**
	 * Return if the specified tasktracker is in the exclude list.
	 */
	private boolean inExcludedHostsList(TaskTrackerStatus status) {
		Set<String> excludeList = hostsReader.getExcludedHosts();
		return excludeList.contains(status.getHost());
	}

	/**
	 * Returns true if the tasktracker is in the hosts list and not in the
	 * exclude list.
	 */
	private boolean acceptTaskTracker(TaskTrackerStatus status) {
		return (inHostsList(status) && !inExcludedHostsList(status));
	}

	/**
	 * Update the last recorded status for the given task tracker. It assumes
	 * that the taskTrackers are locked on entry.
	 * 
	 * @param trackerName
	 *            The name of the tracker
	 * @param status
	 *            The new status for the task tracker
	 * @return Was an old status found?
	 */
	private boolean updateTaskTrackerStatus(String trackerName,
			TaskTrackerStatus status) {
		TaskTrackerStatus oldStatus = taskTrackers.get(trackerName);
		if (oldStatus != null) {
			totalMaps -= oldStatus.countMapTasks();
			totalReduces -= oldStatus.countReduceTasks();
			if (!faultyTrackers.isBlacklisted(oldStatus.getHost())) {
				totalMapTaskCapacity -= oldStatus.getMaxMapTasks();
				totalReduceTaskCapacity -= oldStatus.getMaxReduceTasks();
			}
			if (status == null) {
				taskTrackers.remove(trackerName);
				Integer numTaskTrackersInHost = uniqueHostsMap.get(oldStatus
						.getHost());
				numTaskTrackersInHost--;
				if (numTaskTrackersInHost > 0) {
					uniqueHostsMap.put(oldStatus.getHost(),
							numTaskTrackersInHost);
				} else {
					uniqueHostsMap.remove(oldStatus.getHost());
				}
			}
		}
		if (status != null) {
			totalMaps += status.countMapTasks();
			totalReduces += status.countReduceTasks();
			if (!faultyTrackers.isBlacklisted(status.getHost())) {
				totalMapTaskCapacity += status.getMaxMapTasks();
				totalReduceTaskCapacity += status.getMaxReduceTasks();
			}
			boolean alreadyPresent = false;
			if (taskTrackers.containsKey(trackerName)) {
				alreadyPresent = true;
			}
			taskTrackers.put(trackerName, status);

			if (!alreadyPresent) {
				Integer numTaskTrackersInHost = uniqueHostsMap.get(status
						.getHost());
				if (numTaskTrackersInHost == null) {
					numTaskTrackersInHost = 0;
				}
				numTaskTrackersInHost++;
				uniqueHostsMap.put(status.getHost(), numTaskTrackersInHost);
			}
		}
		return oldStatus != null;
	}

	/**
	 * Process incoming heartbeat messages from the task trackers.
	 */
	private synchronized boolean processHeartbeat(
			TaskTrackerStatus trackerStatus, boolean initialContact) {
		String trackerName = trackerStatus.getTrackerName();

		synchronized (taskTrackers) {
			synchronized (trackerExpiryQueue) {
				boolean seenBefore = updateTaskTrackerStatus(trackerName,
						trackerStatus);
				if (initialContact) {
					// If it's first contact, then clear out
					// any state hanging around
					if (seenBefore) {
						lostTaskTracker(trackerName);
					}
				} else {
					// If not first contact, there should be some record of the
					// tracker
					if (!seenBefore) {
						LOG
								.warn("Status from unknown Tracker : "
										+ trackerName);
						updateTaskTrackerStatus(trackerName, null);
						return false;
					}
				}

				if (initialContact) {
					// if this is lost tracker that came back now, and if it
					// blacklisted
					// increment the count of blacklisted trackers in the
					// cluster
					if (isBlacklisted(trackerName)) {
						faultyTrackers.numBlacklistedTrackers += 1;
					}
					addNewTracker(trackerStatus);
				}
			}
		}

		updateTaskStatuses(trackerStatus);

		return true;
	}

	/**
	 * A tracker wants to know if any of its Tasks have been closed (because the
	 * job completed, whether successfully or not)
	 */
	private synchronized List<TaskTrackerAction> getTasksToKill(
			String taskTracker) {

		Set<TaskAttemptID> taskIds = trackerToTaskMap.get(taskTracker);
		List<TaskTrackerAction> killList = new ArrayList<TaskTrackerAction>();
		if (taskIds != null) {
			for (TaskAttemptID killTaskId : taskIds) {
				TaskInProgress tip = taskidToTIPMap.get(killTaskId);
				if (tip == null) {
					continue;
				}
				if (tip.shouldClose(killTaskId)) {
					// 
					// This is how the JobTracker ends a task at the
					// TaskTracker.
					// It may be successfully completed, or may be killed in
					// mid-execution.
					//
					if (!tip.getJob().isComplete()) {
						killList.add(new KillTaskAction(killTaskId));
						LOG.debug(taskTracker + " -> KillTaskAction: "
								+ killTaskId);
					}
				}
			}
		}

		// add the stray attempts for uninited jobs
		synchronized (trackerToTasksToCleanup) {
			Set<TaskAttemptID> set = trackerToTasksToCleanup
					.remove(taskTracker);
			if (set != null) {
				for (TaskAttemptID id : set) {
					killList.add(new KillTaskAction(id));
				}
			}
		}
		return killList;
	}

	/**
	 * Add a job to cleanup for the tracker.
	 */
	private void addJobForCleanup(JobID id) {
		for (String taskTracker : taskTrackers.keySet()) {
			LOG.debug("Marking job " + id + " for cleanup by tracker "
					+ taskTracker);
			synchronized (trackerToJobsToCleanup) {
				Set<JobID> jobsToKill = trackerToJobsToCleanup.get(taskTracker);
				if (jobsToKill == null) {
					jobsToKill = new HashSet<JobID>();
					trackerToJobsToCleanup.put(taskTracker, jobsToKill);
				}
				jobsToKill.add(id);
			}
		}
	}

	/**
	 * A tracker wants to know if any job needs cleanup because the job
	 * completed.
	 */
	private List<TaskTrackerAction> getJobsForCleanup(String taskTracker) {
		Set<JobID> jobs = null;
		synchronized (trackerToJobsToCleanup) {
			jobs = trackerToJobsToCleanup.remove(taskTracker);
		}
		if (jobs != null) {
			// prepare the actions list
			List<TaskTrackerAction> killList = new ArrayList<TaskTrackerAction>();
			for (JobID killJobId : jobs) {
				killList.add(new KillJobAction(killJobId));
				LOG.debug(taskTracker + " -> KillJobAction: " + killJobId);
			}

			return killList;
		}
		return null;
	}

	/**
	 * A tracker wants to know if any of its Tasks can be committed
	 */
	private synchronized List<TaskTrackerAction> getTasksToSave(
			TaskTrackerStatus tts) {
		List<TaskStatus> taskStatuses = tts.getTaskReports();
		if (taskStatuses != null) {
			List<TaskTrackerAction> saveList = new ArrayList<TaskTrackerAction>();
			for (TaskStatus taskStatus : taskStatuses) {
				if (taskStatus.getRunState() == TaskStatus.State.COMMIT_PENDING) {
					TaskAttemptID taskId = taskStatus.getTaskID();
					TaskInProgress tip = taskidToTIPMap.get(taskId);
					if (tip == null) {
						continue;
					}
					if (tip.shouldCommit(taskId)) {
						saveList.add(new CommitTaskAction(taskId));
						LOG.debug(tts.getTrackerName()
								+ " -> CommitTaskAction: " + taskId);
					}
				}
			}
			return saveList;
		}
		return null;
	}

	// returns cleanup tasks first, then setup tasks.
	private synchronized List<Task> getSetupAndCleanupTasks(
			TaskTrackerStatus taskTracker) throws IOException {
		int maxMapTasks = taskTracker.getMaxMapTasks();
		int maxReduceTasks = taskTracker.getMaxReduceTasks();
		int numMaps = taskTracker.countMapTasks();
		int numReduces = taskTracker.countReduceTasks();
		int numTaskTrackers = getClusterStatus().getTaskTrackers();
		int numUniqueHosts = getNumberOfUniqueHosts();

		Task t = null;
		synchronized (jobs) {
			if (numMaps < maxMapTasks) {
				for (Iterator<JobInProgress> it = jobs.values().iterator(); it
						.hasNext();) {
					JobInProgress job = it.next();
					t = job.obtainJobCleanupTask(taskTracker, numTaskTrackers,
							numUniqueHosts, true);
					if (t != null) {
						return Collections.singletonList(t);
					}
				}
				for (Iterator<JobInProgress> it = jobs.values().iterator(); it
						.hasNext();) {
					JobInProgress job = it.next();
					t = job.obtainTaskCleanupTask(taskTracker, true);
					if (t != null) {
						return Collections.singletonList(t);
					}
				}
				for (Iterator<JobInProgress> it = jobs.values().iterator(); it
						.hasNext();) {
					JobInProgress job = it.next();
					t = job.obtainJobSetupTask(taskTracker, numTaskTrackers,
							numUniqueHosts, true);
					if (t != null) {
						return Collections.singletonList(t);
					}
				}
			}
			if (numReduces < maxReduceTasks) {
				for (Iterator<JobInProgress> it = jobs.values().iterator(); it
						.hasNext();) {
					JobInProgress job = it.next();
					t = job.obtainJobCleanupTask(taskTracker, numTaskTrackers,
							numUniqueHosts, false);
					if (t != null) {
						return Collections.singletonList(t);
					}
				}
				for (Iterator<JobInProgress> it = jobs.values().iterator(); it
						.hasNext();) {
					JobInProgress job = it.next();
					t = job.obtainTaskCleanupTask(taskTracker, false);
					if (t != null) {
						return Collections.singletonList(t);
					}
				}
				for (Iterator<JobInProgress> it = jobs.values().iterator(); it
						.hasNext();) {
					JobInProgress job = it.next();
					t = job.obtainJobSetupTask(taskTracker, numTaskTrackers,
							numUniqueHosts, false);
					if (t != null) {
						return Collections.singletonList(t);
					}
				}
			}
		}
		return null;
	}

	/**
	 * Grab the local fs name
	 */
	public synchronized String getFilesystemName() throws IOException {
		if (fs == null) {
			throw new IllegalStateException(
					"FileSystem object not available yet");
		}
		return fs.getUri().toString();
	}

	public void reportTaskTrackerError(String taskTracker, String errorClass,
			String errorMessage) throws IOException {
		LOG.warn("Report from " + taskTracker + ": " + errorMessage);
	}

	/**
	 * Remove the job_ from jobids to get the unique string.
	 */
	static String getJobUniqueString(String jobid) {
		return jobid.substring(4);
	}

	// //////////////////////////////////////////////////
	// JobSubmissionProtocol
	// //////////////////////////////////////////////////

	/**
	 * Allocates a new JobId string.
	 */
	public synchronized JobID getNewJobId() throws IOException {
		return new JobID(getTrackerIdentifier(), nextJobId++);
	}

	/**
	 * JobTracker.submitJob() kicks off a new job.
	 * 
	 * Create a 'JobInProgress' object, which contains both JobProfile and
	 * JobStatus. Those two sub-objects are sometimes shipped outside of the
	 * JobTracker. But JobInProgress adds info that's useful for the JobTracker
	 * alone.
	 */
	public synchronized JobStatus submitJob(JobID jobId) throws IOException {
		if (jobs.containsKey(jobId)) {
			// job already running, don't start twice
			return jobs.get(jobId).getStatus();
		}

		JobInProgress job = new JobInProgress(jobId, this, this.conf);

		String queue = job.getProfile().getQueueName();
		if (!(queueManager.getQueues().contains(queue))) {
			new CleanupQueue()
					.addToQueue(conf, getSystemDirectoryForJob(jobId));
			throw new IOException("Queue \"" + queue + "\" does not exist");
		}

		// check for access
		try {
			checkAccess(job, QueueManager.QueueOperation.SUBMIT_JOB);
		} catch (IOException ioe) {
			LOG.warn("Access denied for user " + job.getJobConf().getUser()
					+ ". Ignoring job " + jobId, ioe);
			new CleanupQueue()
					.addToQueue(conf, getSystemDirectoryForJob(jobId));
			throw ioe;
		}

		// Check the job if it cannot run in the cluster because of invalid
		// memory
		// requirements.
		try {
			checkMemoryRequirements(job);
		} catch (IOException ioe) {
			new CleanupQueue()
					.addToQueue(conf, getSystemDirectoryForJob(jobId));
			throw ioe;
		}

		return addJob(jobId, job);
	}

	/**
	 * Adds a job to the jobtracker. Make sure that the checks are inplace
	 * before adding a job. This is the core job submission logic
	 * 
	 * @param jobId
	 *            The id for the job submitted which needs to be added
	 */
	private synchronized JobStatus addJob(JobID jobId, JobInProgress job) {
		totalSubmissions++;

		synchronized (jobs) {
			synchronized (taskScheduler) {
				jobs.put(job.getProfile().getJobID(), job);
				for (JobInProgressListener listener : jobInProgressListeners) {
					try {
						listener.jobAdded(job);
					} catch (IOException ioe) {
						LOG.warn("Failed to add and so skipping the job : "
								+ job.getJobID() + ". Exception : " + ioe);
					}
				}
			}
		}
		myInstrumentation.submitJob(job.getJobConf(), jobId);
		return job.getStatus();
	}

	// Check whether the specified operation can be performed
	// related to the job.
	private void checkAccess(JobInProgress job, QueueManager.QueueOperation oper)
			throws IOException {
		// get the user group info
		UserGroupInformation ugi = UserGroupInformation.getCurrentUGI();
		checkAccess(job, oper, ugi);
	}

	// use the passed ugi for checking the access
	private void checkAccess(JobInProgress job,
			QueueManager.QueueOperation oper, UserGroupInformation ugi)
			throws IOException {
		// get the queue
		String queue = job.getProfile().getQueueName();
		if (!queueManager.hasAccess(queue, job, oper, ugi)) {
			throw new AccessControlException("User " + ugi.getUserName()
					+ " cannot perform " + "operation " + oper + " on queue "
					+ queue);
		}
	}

	/** @deprecated use {@link #getClusterStatus(boolean)} */
	@Deprecated
	public synchronized ClusterStatus getClusterStatus() {
		return getClusterStatus(false);
	}

	public synchronized ClusterStatus getClusterStatus(boolean detailed) {
		synchronized (taskTrackers) {
			if (detailed) {
				List<List<String>> trackerNames = taskTrackerNames();
				return new ClusterStatus(trackerNames.get(0), trackerNames
						.get(1), TASKTRACKER_EXPIRY_INTERVAL, totalMaps,
						totalReduces, totalMapTaskCapacity,
						totalReduceTaskCapacity, state);
			} else {
				return new ClusterStatus(taskTrackers.size()
						- getBlacklistedTrackerCount(),
						getBlacklistedTrackerCount(),
						TASKTRACKER_EXPIRY_INTERVAL, totalMaps, totalReduces,
						totalMapTaskCapacity, totalReduceTaskCapacity, state);
			}
		}
	}

	public synchronized void killJob(JobID jobid) throws IOException {
		if (null == jobid) {
			LOG.info("Null jobid object sent to JobTracker.killJob()");
			return;
		}

		JobInProgress job = jobs.get(jobid);

		if (null == job) {
			LOG.info("killJob(): JobId " + jobid.toString()
					+ " is not a valid job");
			return;
		}

		checkAccess(job, QueueManager.QueueOperation.ADMINISTER_JOBS);
		killJob(job);
	}

	private synchronized void killJob(JobInProgress job) {
		LOG.info("Killing job " + job.getJobID());
		JobStatus prevStatus = (JobStatus) job.getStatus().clone();
		job.kill();

		// Inform the listeners if the job is killed
		// Note :
		// If the job is killed in the PREP state then the listeners will be
		// invoked
		// If the job is killed in the RUNNING state then cleanup tasks will be
		// launched and the updateTaskStatuses() will take care of it
		JobStatus newStatus = (JobStatus) job.getStatus().clone();
		if (prevStatus.getRunState() != newStatus.getRunState()
				&& newStatus.getRunState() == JobStatus.KILLED) {
			JobStatusChangeEvent event = new JobStatusChangeEvent(job,
					EventType.RUN_STATE_CHANGED, prevStatus, newStatus);
			updateJobInProgressListeners(event);
		}
	}

	public void initJob(JobInProgress job) {
		if (null == job) {
			LOG.info("Init on null job is not valid");
			return;
		}

		try {
			JobStatus prevStatus = (JobStatus) job.getStatus().clone();
			LOG.info("Initializing " + job.getJobID());
			job.initTasks();
			// Inform the listeners if the job state has changed
			// Note : that the job will be in PREP state.
			JobStatus newStatus = (JobStatus) job.getStatus().clone();
			if (prevStatus.getRunState() != newStatus.getRunState()) {
				JobStatusChangeEvent event = new JobStatusChangeEvent(job,
						EventType.RUN_STATE_CHANGED, prevStatus, newStatus);
				synchronized (JobTracker.this) {
					updateJobInProgressListeners(event);
				}
			}
		} catch (KillInterruptedException kie) {
			// If job was killed during initialization, job state will be KILLED
			LOG.error("Job initialization interrupted:\n"
					+ StringUtils.stringifyException(kie));
			killJob(job);
		} catch (Throwable t) {
			// If the job initialization is failed, job state will be FAILED
			LOG.error("Job initialization failed:\n"
					+ StringUtils.stringifyException(t));
			failJob(job);
		}
	}

	/**
	 * Fail a job and inform the listeners. Other components in the framework
	 * should use this to fail a job.
	 */
	public synchronized void failJob(JobInProgress job) {
		if (null == job) {
			LOG.info("Fail on null job is not valid");
			return;
		}

		JobStatus prevStatus = (JobStatus) job.getStatus().clone();
		LOG.info("Failing job " + job.getJobID());
		job.fail();

		// Inform the listeners if the job state has changed
		JobStatus newStatus = (JobStatus) job.getStatus().clone();
		if (prevStatus.getRunState() != newStatus.getRunState()) {
			JobStatusChangeEvent event = new JobStatusChangeEvent(job,
					EventType.RUN_STATE_CHANGED, prevStatus, newStatus);
			updateJobInProgressListeners(event);
		}
	}

	/**
	 * Set the priority of a job
	 * 
	 * @param jobid
	 *            id of the job
	 * @param priority
	 *            new priority of the job
	 */
	public synchronized void setJobPriority(JobID jobid, String priority)
			throws IOException {
		JobInProgress job = jobs.get(jobid);
		if (null == job) {
			LOG.info("setJobPriority(): JobId " + jobid.toString()
					+ " is not a valid job");
			return;
		}
		checkAccess(job, QueueManager.QueueOperation.ADMINISTER_JOBS);
		JobPriority newPriority = JobPriority.valueOf(priority);
		setJobPriority(jobid, newPriority);
	}

	void storeCompletedJob(JobInProgress job) {
		// persists the job info in DFS
		completedJobStatusStore.store(job);
	}

	public JobProfile getJobProfile(JobID jobid) {
		synchronized (this) {
			JobInProgress job = jobs.get(jobid);
			if (job != null) {
				return job.getProfile();
			}
		}
		return completedJobStatusStore.readJobProfile(jobid);
	}

	public JobStatus getJobStatus(JobID jobid) {
		if (null == jobid) {
			LOG
					.warn("JobTracker.getJobStatus() cannot get status for null jobid");
			return null;
		}
		synchronized (this) {
			JobInProgress job = jobs.get(jobid);
			if (job != null) {
				return job.getStatus();
			}
		}
		return completedJobStatusStore.readJobStatus(jobid);
	}

	public Counters getJobCounters(JobID jobid) {
		synchronized (this) {
			JobInProgress job = jobs.get(jobid);
			if (job != null) {
				return job.getCounters();
			}
		}
		return completedJobStatusStore.readCounters(jobid);
	}

	public synchronized TaskReport[] getMapTaskReports(JobID jobid) {
		JobInProgress job = jobs.get(jobid);
		if (job == null) {
			return new TaskReport[0];
		} else {
			Vector<TaskReport> reports = new Vector<TaskReport>();
			Vector<TaskInProgress> completeMapTasks = job
					.reportTasksInProgress(true, true);
			for (Iterator it = completeMapTasks.iterator(); it.hasNext();) {
				TaskInProgress tip = (TaskInProgress) it.next();
				reports.add(tip.generateSingleReport());
			}
			Vector<TaskInProgress> incompleteMapTasks = job
					.reportTasksInProgress(true, false);
			for (Iterator it = incompleteMapTasks.iterator(); it.hasNext();) {
				TaskInProgress tip = (TaskInProgress) it.next();
				reports.add(tip.generateSingleReport());
			}
			return reports.toArray(new TaskReport[reports.size()]);
		}
	}

	public synchronized TaskReport[] getReduceTaskReports(JobID jobid) {
		JobInProgress job = jobs.get(jobid);
		if (job == null) {
			return new TaskReport[0];
		} else {
			Vector<TaskReport> reports = new Vector<TaskReport>();
			Vector completeReduceTasks = job.reportTasksInProgress(false, true);
			for (Iterator it = completeReduceTasks.iterator(); it.hasNext();) {
				TaskInProgress tip = (TaskInProgress) it.next();
				reports.add(tip.generateSingleReport());
			}
			Vector incompleteReduceTasks = job.reportTasksInProgress(false,
					false);
			for (Iterator it = incompleteReduceTasks.iterator(); it.hasNext();) {
				TaskInProgress tip = (TaskInProgress) it.next();
				reports.add(tip.generateSingleReport());
			}
			return reports.toArray(new TaskReport[reports.size()]);
		}
	}

	public synchronized TaskReport[] getCleanupTaskReports(JobID jobid) {
		JobInProgress job = jobs.get(jobid);
		if (job == null) {
			return new TaskReport[0];
		} else {
			Vector<TaskReport> reports = new Vector<TaskReport>();
			Vector<TaskInProgress> completeTasks = job.reportCleanupTIPs(true);
			for (Iterator<TaskInProgress> it = completeTasks.iterator(); it
					.hasNext();) {
				TaskInProgress tip = (TaskInProgress) it.next();
				reports.add(tip.generateSingleReport());
			}
			Vector<TaskInProgress> incompleteTasks = job
					.reportCleanupTIPs(false);
			for (Iterator<TaskInProgress> it = incompleteTasks.iterator(); it
					.hasNext();) {
				TaskInProgress tip = (TaskInProgress) it.next();
				reports.add(tip.generateSingleReport());
			}
			return reports.toArray(new TaskReport[reports.size()]);
		}

	}

	public synchronized TaskReport[] getSetupTaskReports(JobID jobid) {
		JobInProgress job = jobs.get(jobid);
		if (job == null) {
			return new TaskReport[0];
		} else {
			Vector<TaskReport> reports = new Vector<TaskReport>();
			Vector<TaskInProgress> completeTasks = job.reportSetupTIPs(true);
			for (Iterator<TaskInProgress> it = completeTasks.iterator(); it
					.hasNext();) {
				TaskInProgress tip = (TaskInProgress) it.next();
				reports.add(tip.generateSingleReport());
			}
			Vector<TaskInProgress> incompleteTasks = job.reportSetupTIPs(false);
			for (Iterator<TaskInProgress> it = incompleteTasks.iterator(); it
					.hasNext();) {
				TaskInProgress tip = (TaskInProgress) it.next();
				reports.add(tip.generateSingleReport());
			}
			return reports.toArray(new TaskReport[reports.size()]);
		}
	}

	TaskCompletionEvent[] EMPTY_EVENTS = new TaskCompletionEvent[0];

	static final String MAPRED_CLUSTER_MAP_MEMORY_MB_PROPERTY = "mapred.cluster.map.memory.mb";
	static final String MAPRED_CLUSTER_REDUCE_MEMORY_MB_PROPERTY = "mapred.cluster.reduce.memory.mb";

	static final String MAPRED_CLUSTER_MAX_MAP_MEMORY_MB_PROPERTY = "mapred.cluster.max.map.memory.mb";
	static final String MAPRED_CLUSTER_MAX_REDUCE_MEMORY_MB_PROPERTY = "mapred.cluster.max.reduce.memory.mb";

	/*
	 * Returns a list of TaskCompletionEvent for the given job, starting from
	 * fromEventId.
	 * 
	 * @see
	 * org.apache.hadoop.mapred.JobSubmissionProtocol#getTaskCompletionEvents
	 * (java.lang.String, int, int)
	 */
	public synchronized TaskCompletionEvent[] getTaskCompletionEvents(
			JobID jobid, int fromEventId, int maxEvents) throws IOException {
		synchronized (this) {
			JobInProgress job = this.jobs.get(jobid);
			if (null != job) {
				if (job.inited()) {
					return job.getTaskCompletionEvents(fromEventId, maxEvents);
				} else {
					return EMPTY_EVENTS;
				}
			}
		}
		return completedJobStatusStore.readJobTaskCompletionEvents(jobid,
				fromEventId, maxEvents);
	}

	/**
	 * Get the diagnostics for a given task
	 * 
	 * @param taskId
	 *            the id of the task
	 * @return an array of the diagnostic messages
	 */
	public synchronized String[] getTaskDiagnostics(TaskAttemptID taskId)
			throws IOException {

		JobID jobId = taskId.getJobID();
		TaskID tipId = taskId.getTaskID();
		JobInProgress job = jobs.get(jobId);
		if (job == null) {
			throw new IllegalArgumentException("Job " + jobId + " not found.");
		}
		TaskInProgress tip = job.getTaskInProgress(tipId);
		if (tip == null) {
			throw new IllegalArgumentException("TIP " + tipId + " not found.");
		}
		List<String> taskDiagnosticInfo = tip.getDiagnosticInfo(taskId);
		return ((taskDiagnosticInfo == null) ? null : taskDiagnosticInfo
				.toArray(new String[0]));
	}

	/** Get all the TaskStatuses from the tipid. */
	TaskStatus[] getTaskStatuses(TaskID tipid) {
		TaskInProgress tip = getTip(tipid);
		return (tip == null ? new TaskStatus[0] : tip.getTaskStatuses());
	}

	/** Returns the TaskStatus for a particular taskid. */
	TaskStatus getTaskStatus(TaskAttemptID taskid) {
		TaskInProgress tip = getTip(taskid.getTaskID());
		return (tip == null ? null : tip.getTaskStatus(taskid));
	}

	/**
	 * Returns the counters for the specified task in progress.
	 */
	Counters getTipCounters(TaskID tipid) {
		TaskInProgress tip = getTip(tipid);
		return (tip == null ? null : tip.getCounters());
	}

	/**
	 * Returns the configured task scheduler for this job tracker.
	 * 
	 * @return the configured task scheduler
	 */
	TaskScheduler getTaskScheduler() {
		return taskScheduler;
	}

	/**
	 * Returns specified TaskInProgress, or null.
	 */
	public TaskInProgress getTip(TaskID tipid) {
		JobInProgress job = jobs.get(tipid.getJobID());
		return (job == null ? null : job.getTaskInProgress(tipid));
	}

	/** Mark a Task to be killed */
	public synchronized boolean killTask(TaskAttemptID taskid,
			boolean shouldFail) throws IOException {
		TaskInProgress tip = taskidToTIPMap.get(taskid);
		if (tip != null) {
			checkAccess(tip.getJob(),
					QueueManager.QueueOperation.ADMINISTER_JOBS);
			return tip.killTask(taskid, shouldFail);
		} else {
			LOG.info("Kill task attempt failed since task " + taskid
					+ " was not found");
			return false;
		}
	}

	/**
	 * Get tracker name for a given task id.
	 * 
	 * @param taskId
	 *            the name of the task
	 * @return The name of the task tracker
	 */
	public synchronized String getAssignedTracker(TaskAttemptID taskId) {
		return taskidToTrackerMap.get(taskId);
	}

	public JobStatus[] jobsToComplete() {
		return getJobStatus(jobs.values(), true);
	}

	public JobStatus[] getAllJobs() {
		return getJobStatus(jobs.values(), false);
	}

	/**
	 * @see org.apache.hadoop.mapred.JobSubmissionProtocol#getSystemDir()
	 */
	public String getSystemDir() {
		Path sysDir = new Path(conf.get("mapred.system.dir",
				"/tmp/hadoop/mapred/system"));
		return fs.makeQualified(sysDir).toString();
	}

	// /////////////////////////////////////////////////////////////
	// JobTracker methods
	// /////////////////////////////////////////////////////////////
	public JobInProgress getJob(JobID jobid) {
		return jobs.get(jobid);
	}

	// Get the job directory in system directory
	Path getSystemDirectoryForJob(JobID id) {
		return new Path(getSystemDir(), id.toString());
	}

	/**
	 * Change the run-time priority of the given job.
	 * 
	 * @param jobId
	 *            job id
	 * @param priority
	 *            new {@link JobPriority} for the job
	 */
	synchronized void setJobPriority(JobID jobId, JobPriority priority) {
		JobInProgress job = jobs.get(jobId);
		if (job != null) {
			synchronized (taskScheduler) {
				JobStatus oldStatus = (JobStatus) job.getStatus().clone();
				job.setPriority(priority);
				JobStatus newStatus = (JobStatus) job.getStatus().clone();
				JobStatusChangeEvent event = new JobStatusChangeEvent(job,
						EventType.PRIORITY_CHANGED, oldStatus, newStatus);
				updateJobInProgressListeners(event);
			}
		} else {
			LOG.warn("Trying to change the priority of an unknown job: "
					+ jobId);
		}
	}

	// //////////////////////////////////////////////////
	// Methods to track all the TaskTrackers
	// //////////////////////////////////////////////////
	/**
	 * Accept and process a new TaskTracker profile. We might have known about
	 * the TaskTracker previously, or it might be brand-new. All task-tracker
	 * structures have already been updated. Just process the contained tasks
	 * and any jobs that might be affected.
	 */
	void updateTaskStatuses(TaskTrackerStatus status) {
		String trackerName = status.getTrackerName();
		for (TaskStatus report : status.getTaskReports()) {
			report.setTaskTracker(trackerName);
			TaskAttemptID taskId = report.getTaskID();

			// expire it
			expireLaunchingTasks.removeTask(taskId);

			JobInProgress job = getJob(taskId.getJobID());
			if (job == null) {
				// if job is not there in the cleanup list ... add it
				synchronized (trackerToJobsToCleanup) {
					Set<JobID> jobs = trackerToJobsToCleanup.get(trackerName);
					if (jobs == null) {
						jobs = new HashSet<JobID>();
						trackerToJobsToCleanup.put(trackerName, jobs);
					}
					jobs.add(taskId.getJobID());
				}
				continue;
			}

			if (!job.inited()) {
				// if job is not yet initialized ... kill the attempt
				synchronized (trackerToTasksToCleanup) {
					Set<TaskAttemptID> tasks = trackerToTasksToCleanup
							.get(trackerName);
					if (tasks == null) {
						tasks = new HashSet<TaskAttemptID>();
						trackerToTasksToCleanup.put(trackerName, tasks);
					}
					tasks.add(taskId);
				}
				continue;
			}

			TaskInProgress tip = taskidToTIPMap.get(taskId);
			// Check if the tip is known to the jobtracker. In case of a
			// restarted
			// jt, some tasks might join in later
			if (tip != null || hasRestarted()) {
				if (tip == null) {
					tip = job.getTaskInProgress(taskId.getTaskID());
					job.addRunningTaskToTIP(tip, taskId, status, false);
				}

				// Update the job and inform the listeners if necessary
				JobStatus prevStatus = (JobStatus) job.getStatus().clone();
				// Clone TaskStatus object here, because JobInProgress
				// or TaskInProgress can modify this object and
				// the changes should not get reflected in TaskTrackerStatus.
				// An old TaskTrackerStatus is used later in countMapTasks, etc.
				job.updateTaskStatus(tip, (TaskStatus) report.clone());
				JobStatus newStatus = (JobStatus) job.getStatus().clone();

				// Update the listeners if an incomplete job completes
				if (prevStatus.getRunState() != newStatus.getRunState()) {
					JobStatusChangeEvent event = new JobStatusChangeEvent(job,
							EventType.RUN_STATE_CHANGED, prevStatus, newStatus);
					updateJobInProgressListeners(event);
				}
			} else {
				LOG
						.info("Serious problem.  While updating status, cannot find taskid "
								+ report.getTaskID());
			}

			// Process 'failed fetch' notifications
			List<TaskAttemptID> failedFetchMaps = report.getFetchFailedMaps();
			if (failedFetchMaps != null) {
				for (TaskAttemptID mapTaskId : failedFetchMaps) {
					TaskInProgress failedFetchMap = taskidToTIPMap
							.get(mapTaskId);

					if (failedFetchMap != null) {
						// Gather information about the map which has to be
						// failed, if need be
						String failedFetchTrackerName = getAssignedTracker(mapTaskId);
						if (failedFetchTrackerName == null) {
							failedFetchTrackerName = "Lost task tracker";
						}
						failedFetchMap.getJob().fetchFailureNotification(
								failedFetchMap, mapTaskId,
								failedFetchTrackerName);
					}
				}
			}
		}
	}

	/**
	 * We lost the task tracker! All task-tracker structures have already been
	 * updated. Just process the contained tasks and any jobs that might be
	 * affected.
	 */
	void lostTaskTracker(String trackerName) {
		LOG.info("Lost tracker '" + trackerName + "'");

		// remove the tracker from the local structures
		synchronized (trackerToJobsToCleanup) {
			trackerToJobsToCleanup.remove(trackerName);
		}

		synchronized (trackerToTasksToCleanup) {
			trackerToTasksToCleanup.remove(trackerName);
		}

		// Inform the recovery manager
		recoveryManager.unMarkTracker(trackerName);

		Set<TaskAttemptID> lostTasks = trackerToTaskMap.get(trackerName);
		trackerToTaskMap.remove(trackerName);

		if (lostTasks != null) {
			// List of jobs which had any of their tasks fail on this tracker
			Set<JobInProgress> jobsWithFailures = new HashSet<JobInProgress>();
			for (TaskAttemptID taskId : lostTasks) {
				TaskInProgress tip = taskidToTIPMap.get(taskId);
				JobInProgress job = tip.getJob();

				// Completed reduce tasks never need to be failed, because
				// their outputs go to dfs
				// And completed maps with zero reducers of the job
				// never need to be failed.
				if (!tip.isComplete()
						|| (tip.isMapTask() && !tip.isJobSetupTask() && job
								.desiredReduces() != 0)) {
					// if the job is done, we don't want to change anything
					if (job.getStatus().getRunState() == JobStatus.RUNNING
							|| job.getStatus().getRunState() == JobStatus.PREP) {
						// the state will be KILLED_UNCLEAN, if the task(map or
						// reduce)
						// was RUNNING on the tracker
						TaskStatus.State killState = (tip.isRunningTask(taskId)
								&& !tip.isJobSetupTask() && !tip
								.isJobCleanupTask()) ? TaskStatus.State.KILLED_UNCLEAN
								: TaskStatus.State.KILLED;
						job.failTrackerMap = true;
						job.failedTask(tip, taskId,
								("Lost task tracker: " + trackerName), (tip
										.isMapTask() ? TaskStatus.Phase.MAP
										: TaskStatus.Phase.REDUCE), killState,
								trackerName);
						jobsWithFailures.add(job);
					}
				} else {
					// Completed 'reduce' task and completed 'maps' with zero
					// reducers of the job, not failed;
					// only removed from data-structures.
					markCompletedTaskAttempt(trackerName, taskId);
				}
			}

			// Penalize this tracker for each of the jobs which
			// had any tasks running on it when it was 'lost'
			for (JobInProgress job : jobsWithFailures) {
				job.addTrackerTaskFailure(trackerName);
				//job.clearTasksOnFailedTracker(trackerName);
			}
			
			// Purge 'marked' tasks, needs to be done
			// here to prevent hanging references!
			removeMarkedTasks(trackerName);
		}
	}

	/**
	 * Get the localized job file path on the job trackers local file system
	 * 
	 * @param jobId
	 *            id of the job
	 * @return the path of the job conf file on the local file system
	 */
	public static String getLocalJobFilePath(JobID jobId) {
		return JobHistory.JobInfo.getLocalJobFilePath(jobId);
	}

	// //////////////////////////////////////////////////////////
	// main()
	// //////////////////////////////////////////////////////////

	/**
	 * Start the JobTracker process. This is used only for debugging. As a rule,
	 * JobTracker should be run as part of the DFS Namenode process.
	 */
	public static void main(String argv[]) throws IOException,
			InterruptedException {
		StringUtils.startupShutdownMessage(JobTracker.class, argv, LOG);
		if (argv.length != 0) {
			System.out.println("usage: JobTracker");
			System.exit(-1);
		}

		try {
			JobTracker tracker = startTracker(new JobConf());
			tracker.offerService();
		} catch (Throwable e) {
			LOG.fatal(StringUtils.stringifyException(e));
			System.exit(-1);
		}
	}

	@Override
	public JobQueueInfo[] getQueues() throws IOException {
		return queueManager.getJobQueueInfos();
	}

	@Override
	public JobQueueInfo getQueueInfo(String queue) throws IOException {
		return queueManager.getJobQueueInfo(queue);
	}

	@Override
	public JobStatus[] getJobsFromQueue(String queue) throws IOException {
		Collection<JobInProgress> jips = taskScheduler.getJobs(queue);
		return getJobStatus(jips, false);
	}

	private synchronized JobStatus[] getJobStatus(
			Collection<JobInProgress> jips, boolean toComplete) {
		if (jips == null || jips.isEmpty()) {
			return new JobStatus[] {};
		}
		ArrayList<JobStatus> jobStatusList = new ArrayList<JobStatus>();
		for (JobInProgress jip : jips) {
			JobStatus status = jip.getStatus();
			status.setStartTime(jip.getStartTime());
			status.setUsername(jip.getProfile().getUser());
			if (toComplete) {
				if (status.getRunState() == JobStatus.RUNNING
						|| status.getRunState() == JobStatus.PREP) {
					jobStatusList.add(status);
				}
			} else {
				jobStatusList.add(status);
			}
		}
		return (JobStatus[]) jobStatusList.toArray(new JobStatus[jobStatusList
				.size()]);
	}

	/**
	 * Returns the confgiured maximum number of tasks for a single job
	 */
	int getMaxTasksPerJob() {
		return conf.getInt("mapred.jobtracker.maxtasks.per.job", -1);
	}

	@Override
	public void refreshServiceAcl() throws IOException {
		if (!conf
				.getBoolean(
						ServiceAuthorizationManager.SERVICE_AUTHORIZATION_CONFIG,
						false)) {
			throw new AuthorizationException(
					"Service Level Authorization not enabled!");
		}
		SecurityUtil.getPolicy().refresh();
	}

	private void initializeTaskMemoryRelatedConfig() {
		memSizeForMapSlotOnJT = JobConf.normalizeMemoryConfigValue(conf
				.getLong(JobTracker.MAPRED_CLUSTER_MAP_MEMORY_MB_PROPERTY,
						JobConf.DISABLED_MEMORY_LIMIT));
		memSizeForReduceSlotOnJT = JobConf.normalizeMemoryConfigValue(conf
				.getLong(JobTracker.MAPRED_CLUSTER_REDUCE_MEMORY_MB_PROPERTY,
						JobConf.DISABLED_MEMORY_LIMIT));

		if (conf.get(JobConf.UPPER_LIMIT_ON_TASK_VMEM_PROPERTY) != null) {
			LOG
					.warn(JobConf
							.deprecatedString(JobConf.UPPER_LIMIT_ON_TASK_VMEM_PROPERTY)
							+ " instead use "
							+ JobTracker.MAPRED_CLUSTER_MAX_MAP_MEMORY_MB_PROPERTY
							+ " and "
							+ JobTracker.MAPRED_CLUSTER_MAX_REDUCE_MEMORY_MB_PROPERTY);

			limitMaxMemForMapTasks = limitMaxMemForReduceTasks = JobConf
					.normalizeMemoryConfigValue(conf.getLong(
							JobConf.UPPER_LIMIT_ON_TASK_VMEM_PROPERTY,
							JobConf.DISABLED_MEMORY_LIMIT));
			if (limitMaxMemForMapTasks != JobConf.DISABLED_MEMORY_LIMIT
					&& limitMaxMemForMapTasks >= 0) {
				limitMaxMemForMapTasks = limitMaxMemForReduceTasks = limitMaxMemForMapTasks
						/ (1024 * 1024); // Converting old values in bytes to MB
			}
		} else {
			limitMaxMemForMapTasks = JobConf
					.normalizeMemoryConfigValue(conf
							.getLong(
									JobTracker.MAPRED_CLUSTER_MAX_MAP_MEMORY_MB_PROPERTY,
									JobConf.DISABLED_MEMORY_LIMIT));
			limitMaxMemForReduceTasks = JobConf
					.normalizeMemoryConfigValue(conf
							.getLong(
									JobTracker.MAPRED_CLUSTER_MAX_REDUCE_MEMORY_MB_PROPERTY,
									JobConf.DISABLED_MEMORY_LIMIT));
		}

		LOG
				.info(new StringBuilder()
						.append("Scheduler configured with ")
						.append(
								"(memSizeForMapSlotOnJT, memSizeForReduceSlotOnJT,")
						.append(
								" limitMaxMemForMapTasks, limitMaxMemForReduceTasks) (")
						.append(memSizeForMapSlotOnJT).append(", ").append(
								memSizeForReduceSlotOnJT).append(", ").append(
								limitMaxMemForMapTasks).append(", ").append(
								limitMaxMemForReduceTasks).append(")"));
	}

	private boolean perTaskMemoryConfigurationSetOnJT() {
		if (limitMaxMemForMapTasks == JobConf.DISABLED_MEMORY_LIMIT
				|| limitMaxMemForReduceTasks == JobConf.DISABLED_MEMORY_LIMIT
				|| memSizeForMapSlotOnJT == JobConf.DISABLED_MEMORY_LIMIT
				|| memSizeForReduceSlotOnJT == JobConf.DISABLED_MEMORY_LIMIT) {
			return false;
		}
		return true;
	}

	/**
	 * Check the job if it has invalid requirements and throw and IOException if
	 * does have.
	 * 
	 * @param job
	 * @throws IOException
	 */
	private void checkMemoryRequirements(JobInProgress job) throws IOException {
		if (!perTaskMemoryConfigurationSetOnJT()) {
			LOG.debug("Per-Task memory configuration is not set on JT. "
					+ "Not checking the job for invalid memory requirements.");
			return;
		}

		boolean invalidJob = false;
		String msg = "";
		long maxMemForMapTask = job.getJobConf().getMemoryForMapTask();
		long maxMemForReduceTask = job.getJobConf().getMemoryForReduceTask();

		if (maxMemForMapTask == JobConf.DISABLED_MEMORY_LIMIT
				|| maxMemForReduceTask == JobConf.DISABLED_MEMORY_LIMIT) {
			invalidJob = true;
			msg = "Invalid job requirements.";
		}

		if (maxMemForMapTask > limitMaxMemForMapTasks
				|| maxMemForReduceTask > limitMaxMemForReduceTasks) {
			invalidJob = true;
			msg = "Exceeds the cluster's max-memory-limit.";
		}

		if (invalidJob) {
			StringBuilder jobStr = new StringBuilder().append(
					job.getJobID().toString()).append("(").append(
					maxMemForMapTask).append(" memForMapTasks ").append(
					maxMemForReduceTask).append(" memForReduceTasks): ");
			LOG.warn(jobStr.toString() + msg);

			throw new IOException(jobStr.toString() + msg);
		}
	}
}
